The Isopods of the Pacific Coast of North America. 321 



seem to have been well ossified, but much constricted, and all 

 those preserved belong to the abdominal region. Nothing 

 can be added to the description of the dorsal scutes given by 

 Davis ; but appearances suggest that at the broken hinder 

 end of the fossil the row of scutes terminates, while the dorsal 

 fin begins. The only scales shown are those of the two 

 swallowed fishes in the abdoriien. 



On the whole, it seems ])robable \\\\xi PantophoUs will prove 

 to be a member of the same extinct family of Scopeloids as 

 Enchodus. It is remarkable for the length and slenderness 

 of the abdominal region, the large size of the pectoral fins, 

 and the unusually numerous median dorsal scutes. 



XXXIV. — Key to the Isopods of the Pacific Coast of North 

 America, loith Descriptions of Tvoenty-ttco new Species. By 

 Harriet Richardson. 



[Concluded from p. 277.] 



IV. ASELLOTA. 



Analytical Key to the Families of Asellota'^. 



a. Lateral parts of cephalon scarcely expanded. 



Eyes, when present, small, lateral. Peduncle 



of inferior antennre without small accessory 



appendage outside of third joint. Legs nmbula- 



tory, except first pair, which are distinctly sub- 



cbeliform ; legs with dactylus generally uniungui- 



culate. First pair of pleopoda in female very 



small, not operculiform. Outer lamella of second 



pair very large and iucrusted, so as to form, 



together with con-espondiug lamellte of other 



side, a sort of operculum, covering the two suc- 

 ceeding pairs XL Asellid.e. 



a. Lateral parts of cephalon usually lamellarly ex- 

 panded. Eyes, when present, usually subdorsal. 



Peduncle of inferior antennae generally with 



small accessory appendage outside of third joint. 



Legs subequal in length with dactylus, generally 



bi- or triunguiculate ; first pair sometimes 



prehensile. First pair of pleopoda in female 



transformed into a single large opercular plate. 



Outer lamellae of two succeeding pairs narrow 



and confluent with basal part XII. Jaxirid.^. 



* Sars, Crust, of Norway, ii. 1397, pts. 5, 6, pp. 95, 98. 



