STATE GEOLOGIST. 39 



of the head being more marked and the fornicesless prominent. It 

 is difficult to say whether our Minnesota specimens most resemble 

 this or the typical C. reticulata of Europe. They seem intermedi- 

 ate, some having fornices with an abrupt angle. It may be in- 

 structive to quote Karz on the European C. reticulata — "Examples 

 occur 0.8-0.9 mm. long, others on the contrary only 0.5-0.6 mm» 

 long and combining with the smaller size some differential char- 

 acters. In the larger variety I found the fornix obtuse, while in 

 the smaller it extends in a sUarp thorn directed upward and out- 

 ward. In this small sub-species the secondary teeth of the claws 

 of the post-abdomen seemed to be absent, though in C. reticulata 

 3-5 are constantly present." 



Sp. 8. Cerioclaphaia punctata, P. E. Mueller, 

 (Plate A. Figs. 1-3.) 



Head depressed, rounded at the end, not angulated, ornamented 

 With minute spines within the hexagonal areas. Fornices slightly 

 prominent, either smooth or spiny; antennules very long; shell 

 rotund, reticulated; post-abdomen of medium size, width nearly 

 uniform, truncate below at an obtuse aagle; anal spines large, in- 

 creasing toward the end; claws smooth. Length 0.7 — 0.9 mm. 



Found as yet only in Scandinavia, 



Sp. 9. CeriodapJinia laticaudata, P. E. Mueller. 

 (Plate A. Fig. 22.) 



Ceriodaphnia quadrangula, Sars, (fide Mdelt.EK.) 



Head small, depressed, rounded at the end, not angulated; forni- 

 ces prominent; shell roundish, or sub-quadrangular, moderately 

 reticulated; antennules rather large; post-abiomnen broad, nar- 

 rowed from the middle to the end; the nine or ten small anal spines 

 nearly equal ; claws large and smooth. In P. E. Mueller's time 

 males unknown. Length 1 mm. Specimens 0,6 mm. long from 

 Minnesota agree in most respects, but the reticulation is very 

 marked and irregular and the terminal claws are pectinate. This 

 form constitutes a transition to the next. 



A species related to C. laticaudata, but only half the size, was 

 found in Clarke's lake, a small but very deep pool, containing a 

 fauna like that of the great lakes. The appearance is like the 

 small form alluded to under that species, but the claws are smooth, 

 the head is slender and strongly angled behind the eyes, and the 

 antennules are of rather large size. The fornices are not very 



