1902.] CRUSTACEA OF THE " SKEAT EXPEDITION." 373 



B. Carina terminating- in a fork. 



Terga absent. 



Basal segment broader than occludent and of 



tlie same length D. cor Auri v. 



Basal segment narrower than occludent and 

 shorter. 



Basal at right angles to occludent D. aperta Auri v. 



Basal at obtuse angle to occludent, then 



parallel to fork of carina D. ctmeata Auri v. 



Basal segment absent D. angulata Auriv. 



Terga present. 



Basal segment broader than occludent. 



Tergum with three teeth D. alata Auriv. 



Tergum shaped like a horse's head and 



neck D. eqtcina, sp. n. 



Basal segment narrower than occludent. 

 Basal half as long as occludent, or less. 



Tergum triangular D. aj/monini Lessona. 



Tergum with carinal edge rounded, 



scutal edge with 2 lateral teeth D. neptuni Macdonald. 



Basal more than half as long as occludent. 

 Tergum with 2 teeth. 



Teeth nearly equal D. sinuata Auriv. 



Teeth very disproportionate D. tr iff ona Anriv. 



Tergum hook-shaped, handle broad. 



Hook large and blunt D. lowei Darwin. 



Hook small and sharp D. (ferwiwii Pilippi. 



C. Carina terminating in a cup. 



Scutum in two distinct segments. 



Basal narrower than occludent, tergum with 



5 unequal teeth _D. orthogonia Darwin. 



Basal broader than occludent, tergum with 



3 teeth D. occhisa, s^.w. 



Scutum with a notch only and indistinctly divided. D. sessilis Hoek. 



D. Carina absent D. htdlata Auriv, 



28. DicHELASPis occLUSA, sp. nov. (Plate XXXy. figs. 6-6 c.) 



Log. Kelantan ; Trengganu. 



Hah. Mouth-parts of Thenus orientalis. 



The valves in this species are all very closely apposed, much 

 more than in any other species of the genus. The carina extends 

 between the terga by quite 5 of its own length, is rather strongly 

 curved, and has its anterior end expanded, cvip-shaped, and 

 embedded in the peduncle. The scutum consists of two segments, 

 of which the occludent is longer than the basal by barely ^ of its 

 own length, has its tergal margin bluntly rounded, and is united 

 at its rostral end to the basal segment by a narrow bridge of non- 

 calcified tissue ; while the basal is 2| times the breadth of the 

 occludent and separated from it only by a very narrow mem- 

 branous interspace, and is faintly hollowed on its curved carinal 

 margin close to its tergal angle for the reception of the tip of a 

 strong tooth on the tergum. Between this latter tooth and its 

 occludent angle, the tergum is deeply hollowed where it fits round 

 the end of the occludent segment of the scutum ; the scutal 

 margin thus appears tridentate. 



The capitulum is rather flattened from side to side ; the 

 peduncle differs in appearance in the adult and young forms, 

 being in the former swollen, a little shorter than the capitulum, 

 and brown in colour ; and in the latter not swollen, a little longer 



