A large data set, comprising certain measurements of middle ear structures in mammals, was compiled both from measurements made by the author and from the literature. Parameters of the middle ear apparatus believed to be important to audition were compared between fossorial and non-fossorial species, in an attempt to identify general trends among fossorial groups. Although their tympanic membranes are not of unusual size, many fossorial mammals possess enlarged stapes footplate areas, resulting in low anatomical area ratios. Low anatomical lever ratios are also common, and the reduction or loss of middle ear muscles seems to be a consistent trend. These characteristics might be associated with poor sensitivity to airborne sound. Other features of the middle ear apparatus are more variable both between and within fossorial families. The middle ear ossicles of fossorial rodents, talpid moles and some golden moles were not found to differ in mass from those of non-fossorial mammals of similar body size. The similar ossicular morphologies of these animals suggest convergent adaptation towards a subterranean environment, but the middle ear structure alone does not seem to explain the restricted hearing range observed in certain of these species. Some genera of golden moles possess extraordinarily hypertrophied auditory ossicles, which, relative to body mass, are the largest of all mammals for which data are available. These ossicles seem to be adaptations towards a form of inertial bone conduction, used for the detection of substrate vibrations. In stark contrast, the marsupial mole Notoryctes has particularly small ossicles. The unusual middle ear structures of this animal may well be degenerate.

The lungs of the naked mole-rat Heterocephalus glaber were morphologically (qualitatively) and morphometrically (quantitatively) investigated in adult captive in-burrow body-temperature-maintained (CBTMA) and captive cold-exposed animals (CCEA). The observations were compared with those of field (burrow-dwelling) animals (FA) examined in an earlier study. The lungs of the captive animals were morphologically (qualitatively) similar to those of the field mole-rats. Conspicuous paedomorphic features, i.e. a preponderant double pulmonary capillary arrangement, incomplete differentiation of alveolar pneumocytes, and extension of a cuboidal epithelium to the immediate vicinity of the alveoli, were observed. The prevalent pulmonary underdevelopment was attributed to the relatively low metabolic rate of the poikilothermic naked mole-rat, a species that has evolved in a thermally stable environment. Measurable differences and similarities were found between the lungs of the captive naked mole-rats themselves (i.e. the CBTMA and the CCEA) and between the captive and the field ones. Genetic factors may help explain the conserved pulmonary structural features while environmental (gaseous) change from a hypoxic–hypercapneic (an oxygen deficient–high carbon dioxide concentration) to a normoxic–normocapnic atmosphere and the thermal shift respectively may have enforced pulmonary transformations between the CBTMA and the FA and between the CCEA and the CBTMA. Paradoxically, the CCEA had a significantly lower mass-specific total morphometric pulmonary diffusing capacity of 0.024 compared with that of 0.102 mlO2.s−1.mbar−1.kg−1 in the CBTMA. The observed morphometric differences indicate that the lung of the naked mole-rat, though morphologically unchanged, is intrinsically tractable to environmental shifts in its habitat. Studies on captive naked mole-rats should not be indiscriminately taken to be representative of the species.

Macrurous decapod crustaceans are generally uncommon and are often incompletely preserved. However, at certain horizons in the Speeton Clay (Ryazanian–Albian) and Atherfield Clay (Lower Aptian) of Yorkshire and the Isle of Wight respectively, macrurans form the dominant element of the fauna. Two species in particular, Meyeria ornata (Phillips) and Meyerella magna (M'Coy), are not only very common in these formations, but are also very well preserved. Recent collections have yielded a large number of specimens of both species. This material is examined with the aid of SEM techniques, gross morphology is discussed, and the details of the exoskeletons are compared. In the case of M. magna, examples are figured which show traces of a colour pattern and the effects of regeneration on the first pereiopods. A discussion is included of the possible function of the appendages in M. magna and M. ornata, and of their other, unique features. Finally, the mode of life of both species is inferred from a consideration of their morphology, and of the evidence from their preservation, distribution and relationships with associated faunas.