PARASITIC COPEPODA. 205 



Colour of the entire animal, a deep reddish yellow, like that of the gill on which it 

 lives. The two arched halves of the anterior portion of the carapace are almost white, 

 and the uneven line, where the arched portion passes into the flattened plate, stands 

 out prominently in consequence of the meeting of this white colour with the deep 

 yellow. 



Total length 1*1 5 millims. ; length of carapace 0'9 millim. ; length of head 0'5 millim., 

 width of same 0'9 millim.; length of thorax 0*65 millim.; length of egg-strings 

 1*8 millims. 



This Dichelestiid is particularly interesting on account of its peculiar burrowing 

 habit. About fifteen specimens, all females, were obtained from the gill filaments of 

 Tetrodon stellatus. After fastening themselves to the surface of the filament by the 

 prehensile second antennae, and, we strongly suspect, by the terminal hooks on the 

 anal laminae, these parasites in some way irritate the epithelium until it is raised into 

 a broad fold or flap, entirely surrounding the Copepod's body and overlapping its 

 margin on all sides. A small convex mound is thus formed, beneath the open centre 

 of which lies the body of the parasite, its egg- tubes projecting freely and lying along 

 the surface of the gill filament. The anterior margin of the head and the posterior 

 extremity of the body, including the abdomen and anal laminae, are burrowed under 

 the edge of the epithelium fold and fastened by their prehensile hooks. 



Apparently, therefore, the parasite can have no freedom of motion, but is fastened 

 immovably in place. No similar case of burrowing is known to the author ; there are, 

 of course, many genera among the Chondracanthidae and Lernaeidae which bury the 

 head and neck in the flesh of their host. There are also genera of the Dichelestiidae, 

 such as Anthosoma, Eudactylina, and the like, whose prehensile claws irritate the 

 epithelium of the host until it grows up in a fold over the claws themselves. 



But so far as is known, this is the only case where the epithelium folds entirely 

 surround the body, so that the latter is securely held in place by them. The result 

 is that the body of the parasite lies in the bottom of a hole or burrow, with only a 

 portion of its dorsal surface visible. 



Hatschekia, ? n. sp. Plate V., figs. 58 to 60. 



A single specimen of a species belonging to this genus was obtained from the 

 stomach of Carcharias mulleri. It was a young female without egg-strings but with 

 spermatophores, and was only a trifle over 1 millim. in length. 



While it seems to be a new species unlike any thus far described, yet its small size, 

 its poor condition, and the manifest fact that it is not a fully developed adult furnish 

 sufficient reasons to prevent its establishment as a new species. The following 

 description and the figures which accompany it must await future confirmation, 

 therefore, before being finally established. 



Female. Head transversely elliptical, one-half wider than long, one-fifth the 

 entire length. Thorax composed of two free joints and the genital segment. First 



