THE CRUSTACEA OF NEW JERSEY. 147 



Description. — Capitulum very variable, one-fifth longer or less 

 than width. Valves generally approximate, excessively thin, 

 brittle, transparent, colorless, smooth. Scuta with lower part of 

 tergo-carinal edge extremely protuberant. Occludent edge more 

 or less but slightly reflexed, with depressed line extending from 

 umbo to apex, basal edge variably much reflexed, at variable 

 angle, or even to a right angle, thus forming an external rim or 

 collar. No distinct internal teeth, but basal edge under umbones 

 more or less distinctly produced into rounded disc or projection, 

 generally not so much outwardly reflexed as rest of basal edge, 

 and no distinct internal basal rim. Primordial valves usually 

 visible, not lying close to basal edge, but a little above. Terga 

 flat, occludent edge slightly arched, not formed of two sides, apex 

 bent towards carina, and width of lower half very variable. 

 Widest part of tergum from two-thirds to equal width of broadest 

 part of carina below its umbo. Carina very variable, part above 

 umbo either spear-shaped and slightly concave within, or nearly 

 flat with central external ridge. Upper part of carina very and 

 equally narrow, deeply concave within, appears as if only central 

 ridge developed. Part below umbo about one-third whole 

 valve length, generally twice, or even thrice, width of upper 

 part. Disc, or lower part, usually slightly concave within, ex- 

 teriorly with or without central ridge, basal edge rounded and 

 lateral edge more or less curved according to form of upper 

 part. Disc not more deeply imbedded in membrane than upper 

 part of valve. Heel or umbo either angular and prominent, or 

 rounded. Very young with carina simply bowed instead of 

 bent rectangularly. 



Peduncle short, narrow, abruptly inflected all round under basal 

 edges of capitulum, lower part of very variable shape and often 

 suddenly contracted into mere thread which sometimes widens 

 again at extreme end. External membrane very thin, penetrated 

 by usual fine tubuli leading to corium, and wrinkled surface with 

 few or no spines. Peduncle often completely surrounded by yel- 

 lowish ball, sometimes half width of capitulum, formed of very 

 tender vesicular structureless membrane and of pulpy substance. 

 Filamentary appendages five each side, four in pairs at base 



