138 



to be regarded as of generic value,* as has already been stated on page 

 fifty-five of the present volume. 



CORBULA TrASKII? GaBB. 



Plate 17, figure 3. 

 Corbula Traskii, Gabb. — Pal. Cal., Vol. I., p. 149, pi. 22, figs. 121 and 121a. 



Middle Shales, Division D, of the north-west side of Hornby Island ; 

 J. Richardson, 1872. Three imperfectly preserved right valves. 



The sjiecimens are in such poor condition that their determination is 

 far from certain, still Uiey are so much like Mr. Gabb's figures of C. 

 Traskii that their identity with that species is highly probable- The test 

 of these three Corbulce from Hoi-nby Island is more or less coarsely and 

 irregularly striated, rather than oostate, but the sculpture of some 

 Cretaceous species of Corbulce is known to be variable. Thus the valves 

 of C. pyriformis, Meek, good examples of which were collected by Mr. 

 Selwyn in 1875, at Pine River Forks, and on the Upper Peace Eiver, in 

 British Columbia, are indifferently either finely striated or coarsely 

 ribbed. 



Corbula minima, D'Orbigny. 



Plate 17, figures 4 and 4a. 



Corbula minima, D'Orb. Stoliczka — Cret. Pelecyp. S. India, p. 44, pi. 1, figs. 19-22, 



and pi. 16, figs. 7-12. 



Same locality, division and collector as the last ; one right and one left 

 valve, both nearly perfect and well j^reserved. 



The Californian analogue of this species is C. Ilornii of Gabb, which is 

 possibly the same shell as the C. fruncata of D'Orbigny, but not of 

 Sowerby. C. minima has a flatter shell than C. Hornii ; the posterior end 

 of the former is not so much elongated as it is in the latter species, and 

 in C. minima there is an acute urabonal ridge on the posterior end of 

 both valves, which is wanting on the right valve of C. Hornii. 



Periploma suborbiculatum. (N. Sp.) 

 Plate 17, figure 6. 

 Shell inequivalve and inequilateral, compressed at the sides, but some- 

 what tumid in the umbonal region ; test very thin, posterior margin of 

 the valves curved a little to the left ; length slightly greater than the 

 height. Outline subcircular, the lower half of the margin of the valves, 

 in particular, being regularly rounded ; superior border sloping convexly 



* Cretaeeous Pelecypoda of Soutliern India, p. 24. 



