1883.] Heterogenetic Development in Diaptomus. 503 



SiMOCEPHALUS DAPHNOIDES, sp. nov. (Figs. 30, 3 1, Plate V; Fig. 

 16, Plate VI). 



Four nominal speeies of Simocephalus are deseribed : .S. vetu- 

 lus Miiller, vS. expinosiis Koch, ^S. serrtilatus Koch, vS". arnericanus 

 Birge. The differences in some cases seem quite trivial, since the 

 form of the macula nigra certainly varies with age along with the 

 shape and armature of head and the general shape of the body. 

 However, the present species is so unmistakable that it is not 

 requisite to enter upoa a discussion which lack of material 

 makes undesirable. 



Simocephalus daphnoides, sp. nov. — General shape very like Daphnia ; head regu- 

 larly curved and not strongly angled in front, not marked off from the body by a strong 

 depression; eye of moderate size, macula nigra oval to rhomboidal; antennules long 

 curved ; anterior portion of shell as deep as the posterior ; the three curved 

 spines at the lower posterior angle of shell are wanting ; abdomen much as in S. 

 Tjetulus ; claw fringed part way with weak spines. 



This species is recognized by its oval shape and the Daphnia- 

 like shape of head. In old females the spine is about midway of 

 the depth of the shell, but the upper outline is regularly curved 

 and not keeled as in vetuhis (Fig. 29, Plate V). Quite charac- 

 teristic is the absence of the three or four curved, spines on the 

 shell angle (comp. Fig. 31 with 29^^). On the whole in this spe- 

 cies an approach to Daphnia may be seen. Near Decatur, Ala., 

 with Scapholeberis angulata, also in all Southern Alabama. 



Ceriodaphnia alabamensis, sp. nov. (Figs. 11-12. Plate VI). 



Ceriodaphnia is a very perplexing genus, and one in which the 

 effect of age has not been studied. Three species have been 

 mentioned from America, C. cristata Birge, C. consors Birge, and 

 C. teticidata {== dentata Birgo), there remaining /?//^/W/^, rotunda, 

 punctata, laiicauda (?) and quadrangidata, as described in Europe. 



Quite typical C. reticulata were collected back of Paducah, Ky. 

 The peculiar shape of the fornices figured by P. E. Mueller can 

 be produced by pressure. I have little doubt that this is the 

 same animal described from Massachusetts and Wisconsin by 

 Birge. The head is not so suddenly angled behind the eye as 

 figured by Birge, but more so than represented by Mueller. 



C. alaba7nensis, sp. nov. — The form for which this name is 

 offered, is known from a single gathering at Tuscaloosa, Ala., 

 but it differs from any known species so much as to leave no 



