STATE GEOLOGIST. 37 



This species is one of the largest and most readily distinguished 

 as well as rarest of the genus. Very characteristic is the fine an- 

 astomosing striation which breaks up into reticulation only near 

 the shell margins. This species seems to form the transition 

 toward Simocephalus with Scapholeberis, which, however, 

 ■diverges along its own peculiar track. The length is sometimes 1 

 mm. The head is obscurely angulated in front of the antennules, 

 which are large. The antennules of the male are long 

 and have a hooked setse at the end. 



Typical C. megops has not yet been found in America, but the 

 following form takes its place. 



Sp. 2 Ceriodaplinia cristata, Birge. 



The description given by Birge would apply in almost every par- 

 ticular to C. megops, though he seemed to overlook the close con- 

 formity. The size is much less (0.7 mm.), and the post-abdomen 

 «eems more abruptly truncate; moreover the number of anal spines 

 is less. The crest upon the dorsal margin may be the effect of 

 prominences such as are described by P. E. Mueller; at any rate, in 

 view of the fact that but few specimens were discovered, the sug- 

 gestion lies near that C. cristata is the young or, at least, a reduced 

 form of C. megops. 



Found at Southampton, Mass. 



Sp S.—Ceriodaphnia pulcliella, Sars, 



(Plate A, Figs. 14, 19.) 



■Ceriodaphnia pulchella, SARS, P. E. MUELI.BR, KUKZ. 



Very much like C. reticulata, but smaller. Head large, turgid, 

 and angled in front of the antennules, forming almost a right an- 

 gle; fornices moderate; antennules rather large; shell oval, reticu- 

 lated with double contour lines; post-abdomen of medium size, 

 narrowed toward the end, slightly truncate, with about nine spines; 

 terminal claws short, smooth. The flagellum of the male antennae 

 is but slightly hooked,0,5 — 0.6 mm. long. This species is not cer- 

 tainly identified from America, though a form with smooth claws 

 and small fornices occurs with C. dentata in some places. 



Sp. 4. Ceriodaphnia rotunda, Straus. 

 (Plate 13. Fig. ]. Plate A. Figs. 13 and 23.) 



Daphnia rotunda, STRAUS, BAIRD. 



Ceriodaphnia rotunda, Schoedler, Sars, P. E. Mueller', Kurz. 



