1917] The Ottawa Naturalist. 103 



Strophomena sulcata (Verneuil) occurs 10 feet below the base of 

 the cherty Richmond, immediately above the Pholadomorpha pholadi- 

 formis horizon, and also at higher horizons in the argillaceous Rich- 

 mond, associated with Dinorthis subquadrata and Dalmanella jugosa 

 subplicata. 



Zygospira recurvirostris turgida, var. nov., Figs. 15 A, B, C, 

 evidently is closely related to Zygospira recurvirostris (Hall) and 

 Zygospira kentuckiensis James. In all of these forms the plications 

 are subequal in size, the median area of the pedicel valve is not 

 distinctly limited laterally, and the median depression of the brachial 

 valve anteriorly is broad and relatively shallow. In the variety turgida 

 the brachial valve is more convex than in either of the other two forms 

 when specimens of the same small size are compared. The variety 

 evidently is nothing but a Richmond representative of the Trenton 

 species Zygospira recurvirostris. It occurs in the upper part of the 

 argillaceous Richmond. 



Specimens resembling Clidophorus neglectus Hall (Fig. 24), from 

 the Maquoketa of Wisconsin, in outline and general appearance, occur 

 in the cherty Richmond. A much smaller species, Clidophorus 

 noquettensis, sp. nov., Fig. 25, 3 to 4 millimeters in length, is very 

 abundant in certain layers of limestone interbedded with the shales on 

 the lake shore a mile and a half north of the store of J. B. Stratton. 

 This species is referred to Clidophorus on account of the incision made 

 by the clavicular ridge defining the posterior part of the anterior 

 muscular scar, and the absence of any distinct elevation of the casts 

 of this muscular scar in interior casts of this shell, such as occurs 

 commonly in interior casts of typical species of Ctenodonta. The shell 

 is relatvely shorter than in Clidophorus neglectus, and is less produced 

 anterior to the clavicular ridge; the latter is strongly defined and is 

 either vertical or slightly inclined toward the front. In the casts of the 

 interior the beak rises distinctly above the level of the upper margin 

 of that part of the cast which lies anterior to the impression of the 

 clavicular ridge. The umbonal ridge is fairly strong and is sufficiently 

 oblique to give the shell a ctenodontoid appearance. 



In Rominger's list of fossils from the area here discussed, along 

 the east shore of Little Bay de Noquette (Geology of Michigan, vol. I, 

 Part II, 1873, page 52) an undetermined species of Cyrtodonta is 

 included. Specimens' having a general cyrtodontoid appearance occur 

 in the cherty Richmond, and two of these are here figured, but the 

 hinge and teeth are not distinctly defined in the specimens collected so 

 far and hence their generic relations are not definitely determined. 

 One of these, Fig. 22, bears some resemblance in outline to Cyrtodonta 

 affinis, Ulrich, and the other, Fig. 23, to Cyrtodonta persimilis, Ulrich, 

 both of which are Black river forms occurring in the Minnesota area. 



(To be continued) 



