Vol. 69.] 



TWO 1)EEI> BOEINGS Al CALVEEX STATION. 



331 



Fig. 3.— Obolella (?) off. salteri 

 Holl. 



[a — Brachial valve, external view. 

 (Museum of Practical Geology : 

 26235.) Drawn on the basis of 

 a photomicrograph by Mr. H. 

 G. Smith. Tiie stippling repre- 

 sents the portion from which 

 the shell has exfoliated. The 

 drawing is so far diagrammatic 

 that appearances that cannot 

 all be seen by the same illumi- 

 nation are represented on dif- 

 ferent parts of the surface. X 8. 



b = Interior of the umbonal region 

 of another brachial valve. 

 (Museum of Practical Geology : 

 26355.) r l , r 2 = diverging 

 ridges ; m — muscular im- 

 pression. The irregular line to 

 the left of m and the line r 2 

 form the boundaries of the only 

 remaining fragment of the 

 innermost shell-layer. X 9.] 



pedicle-valve having been re- 

 cognized. 



The only information on the 

 internal structure was obtained 

 from two brachial valves, in both 

 of which the innermost shell- 

 layer was lost except close to 

 the umbo. Here may be seen 

 two slight, ridges, diverging at 

 an angle of about 24°; on the 

 outer side of one there are a few 

 striations of muscular attach- 

 ment (m in fig. 3 h). The sub- 

 symmetrical cracks on each side 

 of the umbo, seen in fig. 3«, 

 may have some relation to the 

 internal structure. 



Holl's type appears to be lost, 

 and the most satisfactory account 

 of the species is that given by 

 Dr. Matley, based on topo- 

 types from Malvern. Although 

 Ave are not satisfied that the 

 Calvert species is actually iden- 

 tical with any figured specimen, 

 and had given it a MS. name as a 

 new species ; yet, since the range 

 of form- variation of 0. salteri as 

 figured by Dr. Matley is wide, it 

 seems advisable for the present to 

 leave our specimens under the 

 name 0. (?) aff. salteri Holl. 



The genus Obolella is stated 

 by "Walcott to be confined to the 

 Lower Cambrian ; and the Scan- 

 dinavian forms identified as 0. 

 salteri are placed by him in the 

 new genus (or subgenus of Obolus) 

 Brbygeria. It is by no means 

 certain that these forms are the 

 same as the British species ; 

 therefore we leave the Calvert 

 form under the generic name 

 Obolella (?)> 



1 [Since this paper was read, I have seen Dr. Walcott's Monograph on the 

 Cambrian Brachiopoda (U.S. Geol. Surv. Monogr. vol. li, 1912). Dr. Walcott 

 accepts the Swedish and American type-species of the sub-genus Broggeria 

 Walcott as identical with Obolella salteri Holl. As I am not convinced of 

 the identity of the Calvert species with any of the Swedish and American 

 specimens figured {op. eit. pi. xiii, figs. ] a-'n & pi. xv, figs. 4a-d) I leave the 

 name unaltered. — A. M. D., June 20th, 1913.] 



