SPmiFERID.E. 



109 



Meristella tumida, Dalman (sp.). PI. XI, figs. 1 — 13. 



Terebkatula OBirsA, Soic. Trans. Linn. Soc, vol. xii, p. 516, pi. xxvii, figs. 3, 4, 

 1815. 



Atetpa tcmiua, Hal. Yet. Akad. Handl., p. 134, pi. v, fig. 3, 1828. 

 Teeebratcla tcmida. Von Buck. Ueber Terebrateln, &c., p. 103, 1834. 

 Atkypa tumida, Eisinger. Lethsea Saecica, p. 77, pi. xxii, fig. 5, 1837. 



— TEXUisTRiATA, Sow. Sil. Syst., pi. xii, fig. 3, 1839. 



Terebratula irMiDA, Barrande. Sil. Brach. aus Bohmen ; Xaturw. Abhandl., toI. i, 

 pi. XV, fig. 11, 1847. 



— — Dav. et de Fern. Bull. Soc. Geol. France, 2nd ser., vol. \, pp. 



226 and 246, pi. iii, fig. 26, 184S. 



— — Bronn. IndexPal., p. 1254, 1848. 



Ateypa iriiiDA, Phillips and Salter. Mem. Geol. Surv., vol. ii, p. 279, 1848. 

 Merista — Schmidt. Silar. Format. Ehstland, &c. ; Archiv >"at. Liv- Ehst- und 



Kurlands, vol. ii, p. 209, 1858. 

 Spibigeka — D'Orb. Prodrome, vol. i, p. 43, 1849. 

 Athtbis — M'Coi/. Brit. Pal. Foss., p. 196, 1852. 



— — 2forris. Cat. Brit. Foss., p. 131, 1854. 



— — Salter. SQuria, 2nd edit., pi. xxii, fig. 20, 1859. 



Meristella tumida, J. Hall. Thirteenth Annual Report of the Regents on the State 



Cabinet of New York, p. 73, 1860. 

 Merista — Lindstrom. Ofv. K. Yet. Ak&d. Forhandl.. p. 161, 1S60. 



Spec. C/iar. Shell variable in form, subcircular or rotundo-quadrate, usually a 

 little wider than long; sometimes the width not exceeding the length. Valves almost 

 equally deep and tumid. Dorsal valve uniformly convex to about the middle ; the 

 fold, which is confined to the anterior half, gradually rising from the lateral portions 

 of the shell into a squarish elevation, divided along the middle by an angular 

 depression or groove, which is continued to the umbone. The fold is also usually cur\"ed 

 upwards, so that when viewed in profile the valve is convex from the umbone to 

 about half its length, forming afterwards a concave curve to the extremity of the 

 fold. Ventral valve convex, with a wide square or obtuse sinus, commencing at 

 about the middle of the valve, and extending to the front. It is also divided by a 

 narrow groove, which, originating at the extremity of the beak, extends to the front. 

 The lateral margins are rounded ; front margin straight when the shell is young, but 

 gradually rising, so as to form a rotundato-quadrate lobe towards the dorsal valve : beak 

 small, and so much incur\-ed as to almost touch the umbone of the opposite valve ; no 

 area or foramen visible. Surface of valves smooth, or marked only by fine concentric 

 lines of growth, which are here and there stronger. The interior of the ventral valve is 

 thickened at the beak, and especially for some short distance between the two strong 

 dental plates, which extend along the bottom of the valve by a concavo-convex cune to 



