The notodelphoid copepods parasitic within Ascidians have been generally ignored for a long time. In May 1932 the present writer collected a considerable number at Millport Marine Biological Station, and was amazed at the frequency with which they occur. It may be that the Clyde area is especially favourable to their development, or it may be that the season was particularly good, for about thirty specimens were collected of ten species, of which at least one—the subject of the present paper—was new to science. If this abundance of forms is indeed usual, it is difficult to understand why records are not more frequent, and it would be interesting to learn how frequently these fascinating and aberrant forms are lost in the course of class dissections of their hosts.