DECAPODS SI 
SPIRONTOCARIS TRIDENS Rathbun. 
Spirontocaris tridens RATHBUN, Proc. U. S. Nat. Mus., xxIv, 896, 1902. 
Allied to S. gracilis, S. flexa, and S. decora, but more robust than 
these. 
Female.—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 eae Fic. 34. Spitvontocaris tridens. 2. Station 2865. a@. Side of carapace and 
riorly and isarmed abdomen (xX 13). 4. Dorsal view of anterior portion (x 3). 

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 nearly 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 nearly as long as the body; the scale, measured along 
its outer margin, is a little 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 lies 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 
