408 EEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



tennis G. O. Sars,* but is at once distinguished by the presence of eyes, 

 from which character, as distinctive, the nameP.octilata might be applied 

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



Specimens examined. 



XIII. 



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

 and apparently consisting of only five segments; antennnla 1 and an- 

 tennae short, with evident distinction into peduncle and llagellum; 

 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 

 iransformation 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, 

 b\ 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 antennnla- are 

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

 below them. 



The five pairs of pediforui 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 

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



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



