WHiTlAVES.] FOSSILS OF HAMILTON FORMATION OF ONTARIO 385 



localities, makes the following remarks upon similar specimens collected 

 by himself. " I believe this species to be distinct from & Irimcata. It 

 differs from S. prodactoides in that the dorsal valve is not spinose. S. 

 rockfordensis has a lamellose dorsal valve and is different in shape." 



Orthis (Rhipidomella) Penelope, Hall. 



Orthis Penelope, Hall. 18G0. Thirteenth Rep. N.Y. St. Cab. Nat. Hist., p. 79, figs. 1 

 and 2. 

 Hall. 18U7. Pal. N. York. Vol. IV., p. .50, pi. 6, figs. 2, a-m. 



.. 18S3. Second Ann. Rep., N.Y. St. Geologist, pi. 36, figs. 6-13.! 

 Rhipidomelhi Penelope, Hall and Clarke. 18i)2. Pal. N. York, Vol. VIII., pt. I, pp. 

 211 and 225, pi. 6, figs. 6-13 ; and pi. 6 A, fig. 10 (?11). 



Specimens of a large Orthis (or Rhipidomella), from Bartlett's Mills 

 and Stony Point, Lake Huron, are identified by Mr. Schuchert with 

 Hall's 0. Penelope, but they appear to the writer to be merely adult or 

 large examples of 0. Vanuxemi, Hall. 0. Penelope is probably only a 

 synonym of 0. Vanuxemi, and Mr. Schuchert admits that these two forms 

 " appear to intergrade." 



Pentamerella Pavilionensis (?) Hall. 



Pentamerus papilionensis. Hall. 1860. Thirteenth Rep. N.Y. St. Cab. Nat. Hist., p. 86. 

 Pentameralla papilionensis. Hall. 1867. Pal. N. York, Vol. IV., p. 377, pi. 58, figs.28-37. 

 Pentamerella pavilionensis. Hall and Clarke. 1893. Pal. N. York, Vol. VIII., pt. 2, p. 

 245, pi. 71, figs. 30 and 31. 



Six specimens which are too small or too imperfect to be determined 

 with much certainty, but which are probably referable to this species, 

 have recently been collected at Thedford by Mr. Kernahan. Three of 

 these have both valves more or le.ss well preserved, the others being imper- 

 fect single valves, but none of them show any indication of a fold or sinus. 

 The most perfect of these specimens, which is about ten millimetres and 

 a, half in length, and twelve mm. in breadth, has about eight subangular 

 plications on each valve, which do not reach to the beak. In a larger but 

 very imperfect ventral valve, the plications are more feebly marked and 

 nearly marginal, and the length is apparently a little greater than the 

 height. Some of these specimens are very similar to the shell which 

 Owen figures on Plate 3 A, fig. 1, of the Illustrations to his " Report 

 of a Geological Survey of Wisconsin, Iowa and Minnesota,'' which Mr. 

 Schuchert identifies with Pentamerella dubia, Hall, but in that species 

 the surface is said to be " marked by from fourteen to twenty or more 

 plications.'' 



Gypiddla lteviuscula, Hall. 



Gypidula Iceviuscula, Hall. 1807. Pal. N. York, vol. IV,, p. 381, pi. 58, figs. 22 'and 23. 

 Hall and Clarke. 1893. Pal. N. York, vol. VIII., pt. 2, p. 248, pi 

 72, figs. 25 and 26. 



