FOSSILS OF THE DEVONIAN. 



Ill 



of a ventral valve, where this area and the space occupied by the anterior 

 adductor scars in the dorsal valve is occupied by the short, strong ramuscules 

 from the great sinuses. Over the central portion of the cast the radiating 

 lines of the inner surface of the shell are seen crossing the muscular scars 

 and vascular markings, and somewhat complicate the study of the latter. 

 The draughtsman has represented these, as also all the details, with accuracy. 



On comparing this with the interior of the corresponding valve of 

 Ling da Elder i, of the Trenton limestone of Wisconsin, described by Prof, 

 R P. Whitfield, 8 we observe in the latter the strong extension of the great 

 pallial sinuses nearly around the posterior end of the perivisceral cavity 

 and back of the divaricator scar; the greater anterior expansion of the pal- 

 lial sinuses, and the smaller area of the adjuster muscular scars. The 

 former character is unknown in L. Whitei, but is present in the recent spe- 

 cies so beautifully illustrated by Hancock. 9 



The two paleozoic species possess, however, the large posterior ad- 

 ductor scars, the postero-lateral adjuster scars, and the absence of the inner 

 ramuscules of the posterior extension of the pallial sinuses, features that 

 distinguish them from Lingula anatina and other living species. 



The character of the anterior ramifications of the great sinuses of L. 

 Whitei resembles that of L. affinis more closely than that of any other 

 species. 



To afford the means of a direct comparison between the Silurian, De- 

 vonian, and a recent Lingula, an outline figure of the interior of the dorsal 

 valve of a species from each horizon is given on plate xxi, figs. 18, 19, and 

 20, in which the muscular scars and vascular markings of each are shown. 



The specific name of the Devonian species is given in honor of Dr. C. 

 A. White, geologist and paleontologist. 



Formation and locality. Lower portion of the Devonian limestone, 

 southwest spur of Atrypa Peak, Eureka District, Nevada. 



8 Aruer. Jour. Sci., lid ser., vol. xix, p. 472, 1880. 



9 Organization of the Braclripoda, by Albany Hancock, esq., 1858. Trans. Royal Phil. Soc., pis. 64-66. 



