408 KEPORT OF COMMISSIONER OF FISH AND FISTTr.RIES. 



tenuis G. O. Sars,* but is at once distingiiished by the presence of eyes, 

 from wliicli character, as distinctive, the namGP.ocuhita might be aj)plied 

 to our species if a new trivial name should be thought necessary. 



Specimens examined. 



2099 

 2104 

 2100 

 2105 



2103 



2101 

 2102 

 2106 



Locality. 



Noank Harbor, Conn 



-. do 



OffWatchHiU.R.I. 

 Off Block Island.... 



Vineyard Sound, 



Mass. 



Casco Bay, Me 



...do 



Bay of Fnndy, Grand 



Menan. 



18 

 17-19J 



L. w. 



Bottom. 



Mud. 



Sand 



Sand, mud, and 



stones. 

 Sand 



Mud 



Sand and mud 



When col- 

 lected. 



,187i 



,1874 



July 31, 1874 

 ,1874 



Sept. 8,1871 



July 16, 1873 

 Aug. 4,1873 

 ,1870 



Keceivedfrom — 



Tr.S.rishCom 



...do 



...do 



....do - 



....do 



...do 



. do 



A. E. Verrill . 



Dry. 

 Ale. 



Ale. 

 AIo. 

 Ale. 

 Ale. 



Ale. 



Ale. 

 Ale. 

 Alo. 



XIII.— GNATHIID^. 



Thorax with only five pairs of legs of the normal form in the adults, 

 and apparently consisting of only five segments; antennulse and an- 

 tennae short, with evident distinction into peduncle and flageUum; 

 mouth organs suctorial in the larval state, more or less aborted in the 

 adult; pleon with its segments distinct, bearing the normal number of 

 pleopods ; uropods inserted at the sides of the base of the last segment, 

 biramous and resembling the pleopods but of firmer texture. 



This family is represented on our coast by a number of forms, all of 

 which, however, appear to be referable to a single species, in which, 

 contrary to what is ordinarily observed in the order, a considerable 

 transformation occurs, especially in the males, after the young leave 

 the incubatory pouch, and before they reach the adult form. The 

 sexes are very unlike at maturity, but in both the thorax may be seen, 

 by a little inspection, to consist in reality of seven segments, of which 

 the first is united with the head, but separated from it by a sutural line 

 near its posterior margin, while the seventh is small and resembles the 

 segments of the pleon, which appears as if consisting of seven seg- 

 ments. The last thoracic segment does not bear a pair of legs. The head 

 is large in the adult male and armed with a powerful pair of curved jaws 

 projecting strongly forward and curved upward. The antennulte are 

 short and widely separated at base. The antennse are inserted nearly 

 below them. 



The five pairs of pediform legs are ambulatory and nearly alike 



throughout; the propodal segments are somewhat elongate, and the 



dactyli weak. All the thoracic segments except the first are distinct in 



the male, and aU are distinct in the larval forms, but the fourth and fifth 



• Chr. Vid. Selsk. Forh., 1872, p. 89, foot-note, 1873. 



