88 



Pycnomphalus solaeioides, Hall. (Sp.) 



Plate 13, figs. 3, 3 a, 4-8. 



PUurotomaria solarioides, Hall 1852. Pal. N. Y., vol. II., p. 348, pi. 84, fig. 



4 h, but not 4 a. 

 Nicholson.. 1875. Rep. Pal. Prov. Ont., p. 72, pi. 3, fig. 



15 (?). 

 StraparoUus solarioides, Whitfield. . . . 1882. Geol. Wiscons., vol. IV., p. 358. 



Gait, A. Murray, 1847, and E. Billings, 1857 ; Hespeler, T. C. Weston, 

 1867; Durham, J. Townsend, 1878-82; Elora and Belwood, J. Town- 

 send, 1892. Nicholson (op. cit.) says that P. solarioides is " not uncommon 

 in the Guelph formation of Hespeler, Guelph and Elora.'' 



In the writer's judgment, figure 4a on plate 84 of the second volume 

 of the Palseontology of New York, which is stated to represent the base 

 of a specimen of Pleurotomaria solarioides, represents rather the under 

 side of an imperfect specimen of P. perlata. A number of specimens 

 collected by Mr. Townsend at Durham, Elora and Belwood, which corres- 

 pond perfectly with the other figure (fig. 46) of P. solarioides on plate 84 

 of the volume referred to, have convinced the writer that this species is 

 referable to Lindstrom's genus Pycnomphalus. 



Some of these specimens are mere casts of the interior of the shell. In 

 these the volutions are depressed somewhat obliquely above and regularly 

 rounded beneath. The base appears to be widely and deeply umbilicated, 

 and the inner volutions exposed up to the apex, as represented by fig. 5. 

 Other specimens are casts of the interior, with the test preserved in the 

 umbilical cavity and between the volutions. A section through the centre 

 of one of these, transverse to the volutions, as shown in fig. 6, shows that 

 the inner surface of the latter is encircled by a narrow and slightly 

 recurved prominent spiral ridge, which projects to the centre, leaving 

 open only a narrow spiral umbilical perforation. This spiral ridge was 

 first observed by Mr. Lambe in a natural section of a specimen from Bel- 

 wood. Besides these a few natural moulds of the exterior of the base of 

 the shell, in a dolomitic limestone, have been collected. A gutta-percha 

 impression of one of these moulds from Belwood (fig. 4) shows the char- 

 acters of the lower half of the aperture, the heavy thickening of the inner 

 or columellar lip, the contour of the exterior of the base, with its narrow 

 umbilical perforation, and some indications of the growth lines around 

 the umbilicus. The largest specimen of this species that the writer has 

 seen (the original of fig. 4, on plate 13,) is fifty-one millimetres, or a little 

 more than two inches in its maximum diameter. 



