LOWER SILURIC SHALES OF THE MOHAWK VALLEY 1 09 



cit. plate 83, figures 8a, b, c) shows that owing to the preservation 

 of the specimens the description and original figures are misleading, 

 and the latter quite incorrect. We have for this reason refigured 

 these types (plate 7, figures 3-6). The apex is broken off in 

 both specimens and the scars of the beaks and the growth lines 

 show that the apex was not subcentral as described, but situated 

 well forward. One specimen (type 8a) is obviously flattened and 

 the other much compressed laterally, as shown by the crest and hence 

 too elongate and high. .The surface is nearly smooth and exhibits 

 only obscure finer and a few coarser growth lines. From the type 

 specimens and others from Snake hill we have derived the following 

 description of the species : 



Description. Shell small, broadly subovate in outline, length not 

 quite one-fifth greater than width, slightly wider in front than 

 behind, obliquely subconical, apex situated about one-sixth of the 

 length from the anterior margin, apex hardly incurved, apertural 

 margin arched. In profile view moderately concave below the apex 

 and gently convex behind. Surface markings consisting of fine 

 growth lines and some deeper impressed lines near the margin. 

 Length of type (plate 7, figure 3) 7.5 mm; width (too great) 

 6.2 mm ; height 2.0 + mm - 



Horizon and locality. Snake Hill shale at Snake hill and other 

 localities in Saratoga and Albany counties. 



Remarks. Hall (title 3, page 306) cites his species C. patel- 

 1 i f o r m i s , which is typically based on specimens from the Tren- 

 ton limestone, also from the " semialtered shales near Waterford " 

 without, however, figuring specimens from that locality, his " Hud- 

 son River " type (plate 83, figure 7) coming according to Whitfield 

 and Hovey's Type-catalogue (page 50) from Pulaski and being 

 hence a Lorraine type and quite obviously a species different from 

 Archinacella patelliformis. The Waterford speci- 

 mens differ from A. patelliformis of the Trenton lime- 

 stone in the profile, the anterior line being much deeper cut in the 

 latter species and the apex more protruding and also situated a 

 little more forward ; and in the presence of distinct concentric sur- 

 face lines in that species. Our specimens of A. orbiculata 

 from the Snake Hill beds are all somewhat laterally compressed, 

 as shown by an irregular carina on the posterior slope, but they show 

 quite clearly that this species was wider in front than in 

 A. patelliformis and that probably it is allied to 

 A. del eta Sardeson as figured by Ulrich and Scofield (1897, 

 plate 61, figures 16-20). 



