389 



apparently an adult shell, is about twelve millimetres in length by ten 

 and a half mm. in height. As will be seen by the figure on Plate 46, its 

 marginal outline is rounded subtrigonal and very different to that of the 

 very young and somewhat elongate specimen that was previously figured. 

 As compared with Meek's description of iV! Traskana, its valves are com- 

 pressed rather than ventricose, and its beak is by no means central. 



A left valve of a JVucula, from the roof of the coal at the Nanaimo 

 mines, collected by Mr. Harvey in 1901 and now in the Museum of the 

 Survey, has a somewhat similar outline to the adult Jff. Hornhyense. But 

 the former, which is fifteen millimetres long and a little over twelve high, 

 is marked with very numerous and densely crowded, but very regularly 

 disposed concentric raised lines or minute costulse. 



Dr. Stanton, who has kindly examined ail these specimens, thinks that 

 they are quite distinct from his Nucula Gabbi, " from the upper part of 

 the Knoxville beds about three miles south of Lowerys, Tehama 

 County," * California. 



Nucula Richaedsoni. 



Nucula pectinata, Whiteaves. 1879. This volume, pt. 2, p. 161, pi. 18, fig. 8 ; but not 



Nucula pectinata, J. Sowerby, 1818. 

 Nucula Bichardsoni, Whiteaves. 1896. Trans. Royal Soc. Canada for 1895, Second 

 Series, vol. i, sect, iv, p. 122. 



" Shell similar to iV. pectinata, but less inequilateral and much shorter 

 in proportion to its height, the beaks being more nearly central, the pos- 

 terior side longer and more obliquely truncated, the anterior shorter and 

 more broadly rounded at its outer termination. 



" The slightly distorted valve from the lower part of the Trent River, 

 Vancouver Island, which was referred with doubt to the H. pectinata of 

 Sowerby by the present writer in 1879, appears to be sufficiently distinct 

 from that species to warrant the new specific name now proposed for it, 

 in memory of its discoverer " (1896, op. cit. supra.). 



Nucula (Acila) truncata, Gabb. 



Nucula truncata, Gabb. 1864. Geol. Sur. Calif., Palteont., vol. i, p. 198, pi. 26, figs. 



184 and 184 «, b. 

 Nucula (Acila) truncata, Gabb. 1869. Idem, vol. ii, p. 197. 



Whiteaves. 1879. This volume, pt. 2, p. 162. 



On Vancouver Island, specimens of this species, as determined by the 

 writer, were collected in 1901, from the roof of the coal at the New Van- 



*Bulletin of the U.S. Geographical Survey, No. 133, p. 52. 

 6 — M. F. 



