Morgan Expeditions. 119 



Moderately abundant in the Devonian sandstone of Erere, 

 Prov. of Para, Brazil ; associated with Nuculites Nyssa, 

 Spirifera Pedroana, etc. 



Named after M. Leon Gillet, Prof. Hartt's able and obli's- 

 ins a^ent at Para. 



LAMELLIBRANCHIATA. 



Genus NUCULITES, Conrad. 



Nuculites Nyssa. 



Niiculit.es Nyssa, Hall. Lamell. Shells of the U. Held., Ham. and Chem. 

 Groups, etc., 18(>9. (Preparatory for the Palaeontology of N. Y.) 



Description of Erere specimens: — Shell of medium size, longitudinally 

 sub-ovate or sub-triangular iu outline, and of moderate convexity. Ante- 

 rior margin well rounded and narrower than the posterior. The dorsal 

 margin, curving slightly, extends obliquely backwards from the beak to 

 the posterior extremity of the shell, a short distance above the termina- 

 tion of the median antero-posterior diameter. The ventral margin is mod- 

 erately rounded and, together with the anterior and posterior margins, 

 forms an elliptical curve. Beaks about one-fourth the length from the 

 anterior extremity, with the apices acute and strongly incurved to the 

 hinge line. Valves most convex at a point just above and anterior to the 

 middle. The surface arches rapidly and more or less regularly from 

 the ventral margin to the beak, but is generally a little more strongly 

 curved in the umbonal region, and is broadly flattened, rounding suddenly 

 to the dorsal margin. The slope toward the posterior margin is convex 

 and more abrupt than toward the ventral margin ; toward the anterior 

 margin it is still more abrupt, becoming gradually concave near the beaks. 

 The septum, curving very slightly, and with its concave side forward, 

 extends down nearly two-thirds the shell height, cutting the antero-poste- 

 rior diameter at about one-fourth its length from the front. Surface 

 smooth or marked with a few indistinct lines of growth. Length, 24 mm ; 

 height, 17 mm ; depth of single valve, 5 mm . Specimens of larger size are 

 numerous. 



This species of JVuculiies, which is the most common 

 lamellibranch at Erere, proves to be identical with A 7 ". JSfyssa 

 of Hall, found in the Hamilton group, New York. 



We are indebted to Prof. Hall for the identification of the 

 forms from the two places. 



