DECAPODS 



8i 



SPIRONTOCARIS TRIDENS Rathbun. 

 S^ironfocaris tridens Kkthbv^, Proc. U. S. Nat. Mus., xxiv, 896, 1902. 



Allied to S. gracilis, S. Jlexa, and S. decora, but more robust than 

 these. 



Fetnak.—The median crest occupies the anterior third of the carapace ; 

 superior spines or teeth 3, one on the carapace, one (the largest and 

 highest) over the base of the eye-stalk and nearer to the anterior than to 

 the posterior 

 tooth. In front 

 of the teeth the 

 rostrum has al- 

 most no upper 

 limb and is gently- 

 ascending and 

 slightly curved ; 

 midrib rather stout 

 and acute at tip ; 

 the lower limb 

 diminishes ante- 

 riorly and is armed 



with 3 to 6 teeth, one near the tip. Rostrum longer than the carapace 

 or antennal scale. Anterior margin of carapace furnished with a strong 

 antennal and a very small pterygostomian spine. 



Antennular peduncle extending two fifths the length of the antennal 

 scale ; second and third segments short and subequal ; basal scale with a 

 spine which extends nearly to the end of the second segment. The 

 thickened portion of the outer flagellum reaches neariy to the end of 

 the antennal scale ; inner flagellum twice as long. The antennal pedun- 

 cle extends a little beyond the end of the second antennular segment ; 

 the flagellum is neariy as long as the body ; the scale, measured along 

 its outer margin, is a Uttle shorter than the carapace. 



The maxillipeds reach two thirds the length of the antennal scale ; 

 the first pair of feet barely to the end of the antennal peduncle. The tip 

 of the second pair when extended Hes between the end of the maxilliped 

 and that of the antennal scale ; the tip of the last pair lies between the 

 end of the maxilliped and the antennal peduncle. 



The abdomen has the third segment well produced backward, and its 

 posterior portion carinated ; the carina is defined on either side by a deep 

 groove like the imprint of a nail. The sixth segment is more than twice 

 as long as high, and about as long as the seventh ; this last is a little 



Fig. 34. Sf>irontocaris tridens. 9 . Station 2865. a. Side of carapace and 

 abdomen (X ij). b. Dorsal view of anterior portion (x 3). 



