194 DE. T. DAVIDSON ON EECENT BRACHIOPODA. 



foramen. The valves are also strongly marked with concentric lines or ridges of growth. 

 In the interior of the generally much thickened vipper valve the muscular scars 

 occupy the margins of a rather large sunken space ; there are four obliquely placed 

 adductor scars — two are situated at a short distance from the posterior margin of the 

 valve and are separated by two very small retractor muscular impressions. The second 

 pair of oval-shaped adductor scars are obliquely situated towards the middle of the 

 bottom of the valve, Avith a narrow ridge between them which extends some distance 

 along the bottom of the cavity in the shell. In the interior of the loAver valve the 

 adductor muscular scars meet in front of a small longitudinal septum, which rises 

 from the centre, hiding a small tubular perforation which traverses the valve in an 

 oblique manner ; the posterior adductor scars are small and widely separated. Shell- 

 structure horny and calcareous. Colour yellow and brownish yellow. Length 8^ 

 lines, breadth 8 lines. 



JUab. Cape Palmas, West Africa. 



Ohs. Mr. W. H. Dall has given much attention to the history and identification of the 

 species under description. He states in his Heport on the Brachiopoda obtained by 

 the United States Coast Survey Expedition, loc. cit. p. 40, " when changes in nomen- 

 clature depend upon the identification of types described by the early authors, the 

 work is one of great difiiculty, and requires the utmost caution, lest fresh confusion be 

 the result. In many cases an approximation to a determination alone can be arrived 

 at, and authors may conscientiously difi"er as to the decision, and its bearings on 

 nomenclature. In the present case, however, there is but little difficulty, as the 

 species under consideration has been well described and carefully figured by the 

 describers, though under several names [both generic and specific] ; the history of the 

 type specimens is very clear, and was put on record at the time. 



"Lamarck constituted the genusD/sc/^rt to receive a shell which he called i>. ostreoides, 

 but of which he did not give any figure or specific description. The specimen was 

 received from Mr. J. Sowerby, and is the same species and from the same lot of speci- 

 mens as the shell described by Mr. G. B. Sowerby, in the Linnean 'Transactions,' and 

 well fio-ured by him there, under the name of Orhiciila norvegica. His very excellent 

 fio-vire enables me to speak with positiveness in saying that it is identical with Crania 

 radiosa, Gould, of w^hich the type specimens are before me. The figures of Schumacher 

 are sufficiently exact to allow of identifying the species with his Crania striata. The 

 figures given by Reeve and Davidson are excellent, and almost certainly represent the same 

 species, though this is a matter of little consequence, the main point being the identifica- 

 tion of Sowerby 's shell with the specimens before me, which may be regarded as certain." 



If therefore Schumacher's so termed Crania striata and Lamarck's Discina ostreoides 

 represent the same shell, then of course Schumacher's specific name must be retained for 

 the species. As remarked by Mr. L. Eeeve, the species was named ostreoides by 

 Lamarck from a specimen sent to him in 1819 by Mr. James Sowerby, father of Mr. G. 

 B. Sowerby, who described it in the following year in a paper read before the Linnean 

 Society under the name of Orhicula norvegica. He had then discovered it in abundance 

 in the crevices of a quantity of ballast-stone used in the neighbourhood of Lambeth for 

 mending roads, and it was again described by G. B. Sowerby in 1816, under the name 



