200 PROFESSOR CHARLES CHILTON ON THE 



and having an extremely large side plate. The second and third pleon segments not 

 produced into a postero-dorsal tooth, but the third bearing a stout conical tooth pro- 

 jecting at right angles to the dorsal surface of the segment. The first antenna has the 

 first joint much larger than the second or third, and produced at the upper margin 

 into a broad, hood-like process ; a minute accessory flagellum is present. 



Further Description. The antenna (fig. 12) are quite short, the upper one being 

 slightly longer than the lower. It has its basal joint very stout, and is produced above 

 at the distal end into a broad process overlapping the second and nearly as long. The 

 second joint is slightly broader than the third, which is about the same length. The 

 flagellum tapers gradually, and consists of about thirteen joints, all with very few 

 setae. There is a small accessory appendage. 



In the second antenna the last joint of the peduncle is slightly longer and more 

 slender than the preceding ; the flagellum is of about the same length as the peduncle, 

 and contains about ten joints. 



The mandibles have the same general shape as in Metopa ; the palp, though small, is 

 less vestigial than in some of the other genera of the family ; the first joint is short, the 

 second moderately long and broad, and the third is about as long as the first. There 

 is no molar process. The first maxilla has the palp two-jointed. In the second maxilla 

 the outer lobe is rather longer and broader than the inner. Both these maxilla), and 

 also the maxillipeds, have the same general character as in the next species, T. inermis. 



The first gnathopod (fig. 13) has the basos long, widening a little distally ; the merus 

 is rather longer than the ischium, and ends in a rounded lobe bearing three long setae, 

 the posterior margin being furred ; the carpus is about half as long as the propod, and is 

 produced posteriorly into a short lobe fringed with setse ; the propod sub-oblong, about 

 twice as long as broad, with anterior margin rather strongly convex ; the palm oblique, 

 straight, and defined by stout spinules. 



The second gnathopod (fig. 14) is similar in general structure, but is longer; the 

 ischium is not produced into a lobe ; the carpus is shorter, but has the lobe longer ; and 

 the propod is longer, being considerably more than twice as long as broad. 



The perseopoda are slender, and bear only a few short setae. 



The segments of the urus (fig. 15) cannot be made out distinctly, and appear more 

 or less completely fused ; the uropoda are long and slender, and bear few seta? ; the 

 first uropod reaches beyond the others, and has the peduncle longer than the subequal 

 branches ; in the second uropod the peduncle is about the same length as the equal 

 branches ; the third has the peduncle slightly longer than the basal joint of the single 

 branch. The telson is flattened so as to form a vertical plate, and has a slight 

 thickening along the dorsal margin. 



When the side plates are folded together the strong tooth on the third pleon 

 segment projects backwards, and the whole animal looks very like an Ostracod, some 

 of which were found along with it, having been at first sorted out along with specimens 

 of this species. 



(UOY. SOC. ED1N. TRANS., VOL. XLVIII., 482.) 



