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S. W. Ford — Lower Silurian BracMopoda. 



Art. XLY. — Notice of a new Genus of Lower Silurian Brachi- 

 opoda; by S. W. Ford. 



Several months since Mr. Walter E. Billings, of Ottawa, 

 Canada, sent me a number of wax impressions of the interior 

 of a nearly perfect specimen of the ventral valve of the species 

 described by the late Mr. E. Billings, in 1862, under the name 

 of Ubolella desiderata (Palaeozoic Fossils, vol. i, p. 69). These 

 impressions interested me very much, affording, as they did, 

 more perfect knowledge of the internal structure of this species 

 than had previously been obtained ; and I subsequently re- 

 ceived from Mr. Billings for study, the specimen itself, which 

 belongs to his private collection, accompanied hj the statement 

 that, in case I might so desire, I was at liberty to publish a 

 notice of it. This I some time since resolved to do ; but vari- 

 ous obstacles have prevented, until now, the fulfillment of my 

 intention. 



A careful study of Mr. Billings's specimen, and an examina- 

 tion of the original material used by the late Mr. E. Billings in 

 his description of the species, kindly granted me by Mr. J. F. 

 Whiteaves, have convinced me that 0. desiderata may be taken 

 as the type of a new genus, which will probably include several 

 described Lower Silurian species. It differs from Obolella in 



Genus Billingsia, n. g. 



Eig. ]. — Interior of a nearly perfect specimen of the ventral valve of Billingsia 

 desiderata, enlarged four diameters, aa, cardinal, cc, central and dd lateral mus- 

 cular scars ; g, the groove in the area ; s, the spoon-shaped cavity beneath the 

 beak or rostrum. 



Eig. 2. — Interior of the ventral valve of Obolella crassa Hall sp., enlarged about 

 2-J- diameters, aa, cardinal, cc, central and dd lateral muscular impressions ; g, 

 the groove in the area ; i, pit into which the groove terminates. 



the form and arrangement of its muscular impressions, in the 

 possession of a thinner shell, and in other particulars. For this 

 species I therefore propose a new generic name, Billingsia, in 

 honor of Mr. E. Billings, the late eminent Paleontologist of the 

 Canadian Geological Survey. 



