OF CONCHOLOGY. 91 



Chemnitzia Spillmanni. Mr. Conrad is, possibly, correct in 

 separating this shell from his species. I was obliged to trust 

 almost entirely to my memory, the description being too short 

 and unsatisfactory to assist me. In the description there is 

 no reference to the under side of the whorls; and the differ- 

 ence in the apical angle, between specimens so widely different 

 in age, and, consequently, in size, would not, of itself, be of 

 specific value, unless united with other characters. 



Cardita Hornii. I have already, in my Report, explained 

 the apparently unaccountable mistake into which Mr. Conrad 

 has fallen, with reference to this species. I do not see that 

 there is any thing to add. 



Dosinia elevata is not a Dosiniopsis, but a true Dosinia; so 

 that, despite its external resemblance to I). Meekii, it is still 

 distinct. 



Merelrix Uvasana, Con., [Dosinia, per Err. Jour. Conch.), 

 and Ficus mamillatus, Gabb. Unfortunately, my copy of 

 Conrad's Tert. Foss. is at present inaccessible. I can, conse- 

 quently, express no opinion on these two species; though, if 

 the first is the same as Dione ovata, Rogers, the error is Mr. 

 Conrad's, not mine. 



Meekia sella, G. If Mr. Conrad had taken the pains to have 

 read the generic description, he would have seen at once that 

 this shell, so far from being a Cyprina, could not even belong- 

 to that family. From a long acquaintance with Mr. Conrad, I 

 am convinced that he would not wilfully misrepresent facts, 

 and, consequently, am the more surprised at the extreme care- 

 lessness exhibited by his note on this species. 



Further, he calls it Eocene. Granting that my Division B 

 should prove Eocene, the species would not assist the proof, 

 since, of the three known species of the genus, every specimen 

 yet found has come from the rock which Mr. Conrad says is 

 "doubtless Cretaceous." 



M. navis, G., "is a species of Yoldia." It has the external 

 form of Yoldia, but, nevertheless, has the hinge, and, in a 

 faint degree, the posterior thickening of Meekia. 



Mactra Ashburnerii, G., is a variable species. Mr. Conrad 

 says I have confounded two species, and adds: "One he de- 

 scribes as having 'regular, nearly uniform, rounded, concen- 

 tric ribs,' and another as having only fine lines of growth." 

 In my description (p. 153, Cal. Rep.) I say: "Surface varia- 

 ble ; specimens from some localities showing a large number 

 of regular, nearly uniform, rounded, concentric ribs; while 

 those found at other places have these ribs few, entirely absent, 



