MARYLAND GEOLOGICAL SURVEY 331 



Genus CYRTOGERINA Billings 

 CYRTOCERINA MERCURIUS Billings 



Plate XXXV, Fig. 13 



Cyrtocerina mercurius Billings, 1865, Pal. Foss., vol. i, Geol. Surv. Canada, 

 p. 194, text fig. 179. 



Description. Shell short, strongly curved and tapering abruptly; 

 elliptical in section, the dorso-ventral diameter being one-third or one- 

 fourth greater than the lateral. Measured on the surface of the ventral 

 side near the living chamber the septa are about 1 mm. apart, but on the 

 dorsal side near the apex they are probably closer together. Siphuncle 

 in contact with the shell on its dorsal side. 



The dorsal position of the siphuncle, the close arrangement of the septa, 

 and the strongly curved, abruptly tapering features are characters to aid 

 in the recognition of this shell, although the species cannot be considered 

 to be fully described as yet. 



Occurrence. BEEKMANTOWN LIMESTONE (Turritoma zone). Stouf- 

 ferstown, Pennsylvania, and east of Huyett, Maryland. 



Collection. U. S. National Museum. 



Family ONCOCERATIDAE 



Genus CYCLOSTOMIGERAS Hyatt 



CYCLOSTOMICERAS CASSINENSE (Whitfield) ? 



Plate XXXII, Figs. 6, 7 



Gomphoceras cassinense Whitfield, 1886, Bull. Amer. Mus. Nat. Hist, vol. i, 



p. 322, pi. xxix, figs. 1-3. 

 Cyclostomiceras cassinense Ruedemann, 1906, New York State Mus. Bull., 



No. 90, p. 50, fig. 56; pi. xxxvii, figs. 1-3; pi. xxxviii, figs. 5, 6. 



Description. This species has been carefully described by Euedemann 

 to whose work of 1906 the student is referred for details and illustrations. 

 The entire shell attains a size of about 100 mm. and a greatest width of 

 40 mm. The rate of growth is quite rapid, the living chamber is large, 

 forming nearly half of the shell, the septa are shallow, and the siphuncle 

 is large. Sections in the rock seen at several Maryland outcrops exhibit 

 a cephalopod with the same rate of growth and other characters just 



