188 



Distinguishing Characters,— Nearly round outline; de- 

 pressed convex form; small muscular areas, divided by 



longitudinal median septum. 



Specimens referred to this 

 species, showing the exterior 

 with beak subterminal, and con- 

 centric stria-, are found in the 

 Encrinal limestone, at Section 5. 



Measurements. — Two speci- 



FlG. 00. 



Phoh'dops Oblata. Impres- 

 sion of interior of valve in shale, showing 

 ■ lotiule callosity: exterior of exfoliated ,,,_,,„. l,-......^ 7 QTW 1 G K ,-,,,„ . 



B pecimen, showing submarginal beak, and mens . length, i ami D.O mm., 



a tew lines of growth, Encrinal lime- 

 Motie, x 2%. (Original.; 



width. 0.G and 6.3 mm. 



BRACHIOPODA ARTICULATA. 



Genus RHIP1D0MELLA. Oehlert. 



[Ety. : Ripid, a fan; ella, diminutive.] 

 (Orthis in part.) 



(1891 : Journal de Conchyliologie, p. 372. 1892: Pal. N. Y., Vol. VIII., Pt. 



I., p. 209.) 



Shell almost circular in outline: both valves con vex, brach- 

 ial valve more so than the pedicle valve. Hinge area narrow 

 and short on the brachial valve, higher on the pedicle valve. 

 A slight median depression in each valve. Surface covered 

 with fine, rounded, hollow, tubular stria-, which frequently 

 open upon the surface. On the interior of the pedicle valve 

 appear two strong diverging teeth. Muscular area large, 

 and deeply impressed, consisting of the large fluted diductor 

 impressions, enclosing the small central adductors. The pedi- 

 cle scar fills the cavity of the beak. Outside of the muscular 

 area are commonly deeply-pitted ovarian markings. The 

 interior of the brachial valve shows deep and narrow dental 

 sockets, with prominent projecting crural plates. In the 

 <-'nter is a strong cardinal process, below which is the indis- 

 tinct small muscular area. 



biiirmoMEi.LA vamxkui. Hall. (Fig. 91.) (Pal. N. Y., 

 Vol. IV.. p. 47, PI. VI.) 



