363 



POTAMIDES TENUIS, Gabb. 



Fotamides tenuis, Gabb. 1S64. Geol. Surv. Calif., Palffiont., vol. i, j). 130, pi. 20, fig. 86. 

 Whiteaves. l«7!t. This volume, pt. 2, p. 121, pi. 15, figs. 8 a, 8 «, h. 



The references to this species on page 121 of the second part of this 

 volume are somewhat unfortunate. For, in tlie first place, the two speci- 

 mens from the " ^liddle Shales," one of which is figured, are from the 

 north-west side of Hornby, not. of Denman Island. And in the next 

 place, the two (not three) very small and imperfect specimens from the 

 " Lower Shales " of Denman and the Sucia Islands, prove to be quite 

 distinct from P. tenuis. In Canada, so far as the writer is aware, the 

 typical form of the species, as distinct from the var. Nanaimoensis, has 

 been collected only at Hornby Island, by Mr. Richardson, in 1872 ; at the 

 Sucia Islands, by Dr. Newcombe, in 1894; and from the roof of the coal, 

 Nanaimo mines, V. I., by Mr. Harvey, in 1901. 



In specimens of P. tennis from the Chico group of Fences Ranch, 

 California, the typical locality, kindly lent to the writer for comparison 

 by Dr. Stanton, there are eight volutions. The later ones of the spire 

 are each marked with a spiral row of distant obtusely conical nodes, on 

 the angle near the base, but upon the outer volution these nodes are 

 almost or completely absent. The nodes, also, are much smaller in some 

 specimens than they are in others. In those with very small nodes, the 

 whole of the spire and the upper half of the last volution is ribbed longi- 

 tudinally, that is, in a direction parallel to the main axis, but transversely 

 to each volution. The nodes on the basal angle of the spire of the speci- 

 men from Hornby Island, figured on Plate 15 (figure 8) of the second 

 part of this volume, are unusually large, and they are fully developed on 

 the outer volution. 



Nerinea dispar 1 Gabb. Var. 



Nerinea dispar ? Gabb. Var. Whiteaves. 1896. Ti'ans. Royal See. Canada for 1895, 

 Second Series, vol. i, sect, iv, p. 127, pi. 3, fig. 4. 



" Shell essentially similar in shape and surface markings to JSf. dispar, 

 but smaller and devoid of the rounded spiral fold at the base of each 

 volution said to be characteristic of that species, also with the longitu- 

 dinal ribs apparently obsolete on the lower volutions. 



"Hornby Island, W. Harvey, 1894, three specimens. The most per- 

 fect of these has seven volutions preserved, with the minute details of 

 the sculpture of each quite clearly shewn. The three upper volutions 

 are marked with small longitudinal ribs that cross the volutions trans- 



