414 PROCEEDINGS OF THE NATIONAL MUSEUM. 



dimensions of most of the specimens in the collection average less 

 than those here given. 



The area of the ventral valve is relatively short for a species of this 

 type. It is divided midway, as seen in the cast, by a strong pedicle 

 furrow. Owing to the imperfection of the material, none of the speci- 

 mens show flexure lines or striic of growth. ■ The area of the dorsal 

 valve is short and extends but a short distance on either side of the 

 median line. The cast of the interior of the ventral valve is very much 

 like that of the interior of (). {L.) ci/ane. It has the same median ridge 

 and the transverse trapezoidal area, which includes the central, middle, 

 and outside lateral muscle scars; the main vascular sinuses are indi- 

 cated by slight ridges. The cast of the interior of the dorsal valve 

 shows a narrow median septum, two central muscle scars of average 

 size, situated a short distance back of the center of the shell, and two 

 small anterior lateral scars, located some distance in advance of the 

 center, which gives an elongated visceral cavity somewhat like that of 

 0. (L.) hayesi, of the Middle Cambrian, and (>. (/>.) lamborni, of the 

 Upper Cambrian. 



Ohservaiions. — The external form of the more elongate specimens of 

 this species is very much like that of 0. {L.) acntanf/uhis. When com- 

 pressed laterally it occasionally has the form of Lingulepis acuminatus, 

 and before taking up the detailed study of this group of brachiopods 

 I was led to identify some of the specimens as of tliat species. It is 

 distinguished, however, from all described species of this genus known 

 to me by its highly characteristic surface ornamentation. 0. (L.) stone- 

 anus has the same type of surface, but it differs from the latter in being 

 a much more elongate shell. 



The material studied was collected by Prof. N. S. Shaler and Mr. 

 J. B. Woodworth from the pebbles on the beach on the northern shore 

 of Marthas Vineyard, Massachusetts, and at several points along the 

 shores of Narragansett Bay. The first notice we have of these fos- 

 siliferous pebbles is that of Prof. William B. Rogers, who in 1861 

 announced the discovery, by Mr. Norman Easton, of pebbles carrying 

 fossils of the Potsdam fauna in the Carboniferous conglomerate north 

 of Fall River, Massachusetts. Professor Rogers thought the forms 

 distinctly recognizable as Lingula of two species, Lingula prima and 

 Lingula antiqua Emmons.' 



In 1875 Professor Rogers announced the discovery of impressions 

 suggestive of the fossil Lingulw mentioned by him from Fall River in 

 the pebbles in the conglomerate at Newport, Rhode Island.'- He 

 thought that the pebbles were derived from rocks probably closely 

 connected in time with the Braintree Paridoxides beds. 



Among the material sent by Professor Shaler I found the remains of 



' On Fossiliferous Pebbles of the Potsilani and Carboniferous Conglomerate, North 

 of Fall Kiver, Massathnsetts, Hoston Soc. Nat. Hist. I'roc, ISfil, \'1I, pp. 389-391. 

 H)u the Newport Conglomerate, Boston Soc. Nat. Hist. I'roc., 1875, XVllI, p. 100. 



