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 seem^ to form the transition 

 toward Simocephalus with Scapholebaris, 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 setae at the end. 



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

 following form takes its place. 



Sp. 2 Ceriodaphnia 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 

 seems 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 3. "Ceriodaphnia pulcliella. Sirs, 



(Plate A, Figs. 14, 19,) 

 ■Ceriodaphnia pufchella, SA.BS, P. E. Mueller, Kubz. 



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. Ceriodaplinia rotunda, Straus. 

 (Plate B. Fig. 1, Plate A. Figs. 13 and 23.) 



Dnphnia rotunda, STRAUS, BAIRD. 



Ceriodaphnia rotunda, SCHOEDLER, Sars, P. E. MUELLER, KURZ. 



