KO. 1985. NEW SPECIES OF SILURIAN FOSSILS— WILLIAMS. 335 



more erect and wide, and the anterior ear is larger and not so deeply 

 incut below. Externally the species resembles the Devonian Actin- 

 opterias of Hall, but its well-developed cardinal denticulation sepa- 

 rates it from that genus. 



It differs from Pterinea (sensu stricto) as restricted by me in its 

 development of radial rays and fails to agree with Freeh's group of 

 Pterinea lineata Goldf uss ( = Tolmaia Williams) by its well-developed 

 anterior ear. 



I call it Pterinea {? Tolmaia) trescotti (new species) , using the generic 

 name Pterinea in its broader sense as including rayed as well as smooth 

 shells, since it is evidently a forerunner of the shells of the type of 

 Actinopteria hoydii and A. perstrialis of the Devonian of New York 

 State, but is still in hinge structure one of the Pteriniidse. 



Genus TOLMAIA Williams. 



TOLMAIA CAMPESTRIS, WUliams. 



Plate 29, fig. 16. 



Cf. Avicula reticulataf Hisinger, Sowerby, Sil. Syst., 1839, p. 614, pi. 6, fig. 3. 

 Cf. Pterinea sowerbii M'Coy, Brit. Pal. Rocks and Foss., 1855, p. 263. 



This species bears considerable likeness to Sowerby's figure of 

 Avicula reticulata Hisinger, redescribed under the name Pterinea 

 sowerhyii by M'Coy. It is shorter in form and has a more strongly 

 developed ear, set off from the body of the shell by a distinct byssal 

 sinus. 



The surface markings consist of sharp elevated radii crossed by 

 thin lamellose concentric lines, covering the whole surface of the left 

 valve, including ear and wing, and apparently also the right valve. 

 The interior of both valves is smooth. 



The body of the left valve is convex with moderate development 

 of the umbones, and the deepest part of the shell is near the anterior 

 edge. The posterior side of the body slopes off gradually to the large 

 flat wing. The right valve is less convex than the left over the 

 umbonal region, flattens toward the middle, and turns upward 

 toward the front, making an outwardly concave shell. 



Both cardinal and lateral teeth are present; the outer edge of the 

 hinge is flattened and marked by ligamental striations parallel to the 

 edge. 



The dimensions of the type-specimen are 3 cm wide by 2^ cm high; 

 the largest specimen from the same locality measures 4 by S^ cm. 



Avicula macerata Conrad, figured by Hall from the Niagara group 

 of New York,^ resembles this species, but the surface sculpture of 

 that species on the right valve is limited to ''concentric lines" only 

 on the body and "a few obsolete radiating striae" on the wing. 



I Pal. N. Y., vol. 2, pi. 59, fig. Ic. 



