-■^ 



210 



STALK-EYED CRUSTACEA. 



U 



and unconcealed. The posterior gill of the thirteenth segment is smaller 

 than the anterior gill of the same segment, being a little smaller than the 

 podobranchia attached to the second maxilliped. 



This species bears a close resemblance to Sergesies mollis Smith ^ from the 



4 



Atlantic coast of North America, but differs from the latter species in an 



r 



important structural feature. In 8. mollis the posterior pleurobranchia of 

 the antepenulthnate thoracic somite is replaced by small simple lamella, 

 which is concealed beneath the following gill, while in 8. inous the posterior 

 pleurobranchia of the said somite is well developed and unconcealed. The 

 difference between the two species is at once apparent on lifting the lateral 

 flap of the carapace. 



Sergestes bisulcatus Wood-Masok, 



Plate LIL 



•^ 



^^ 



■^-- 



Sergestes hisulcatm Wood-Mason, Ann. Mag. Nat. Hist., 6th Ser., VII, 190, YIII. 353, 1891. 

 Sergestes phorcus Pax., Bull Mus. Comp. ZooL, XXIV. 217, 1893. 



Carapace devoid of spines ; gastro-hepatic and cervical grooves well pro- 

 nounced across the dorsal part of the carapace ; a ridge runs along the upper 

 border of the branchial area, giving off from its anterior end a branch which 

 runs backward at a lower level along the branchial area; dorsal side of the 

 carapace slightly convex in an antero-posterior sense ; rostrum cristiform, 

 short, laterally compressed, directed obliquely upward, subquadrate in out- 

 line, the anterior margin produced to form a short point near the middle ; 

 antero-lateral margin of the carapace nearly perpendicular from the base of 

 the rostrum to the level of the lower side of the peduncle of the antennule, 

 whence it recedes to an angle over against the base of the second antenna; 

 from this point it becomes concave, sweeping downward and backward^ and 

 forming the ciUated margin of the excurrent branchial orifice. 



The second, third, and more especially the fourth abdominal somites are 

 lightly sulcate in the median dorsal line; the abdominal pleune have rounded, 

 ciliated margins ; the sixth somite is armed with a minute posterior dorsal 

 spine, and is marked by a not very distinct lateral longitudinal sulcus. The 

 telson is sulcate above, and on each side; it is shorter than the sixth abdom- 

 inal segment ; distal end triangular ; margins ciliated. 



The eye-stalky with the eye, is considerably shorter than the proximal 



r 



seo'mcnt of the antennular peduncle; the eye itself is subspherical and much 



' * Ann. Rep, U. S. Fish Comm. for 1882, p. 419, 1884; id. for 1885, Plate XX. Fig. 3, 3«, 4, 5, 188G. 



