313 Systematic Paleontology — Middle Devonian 



Description. — Sliell straight, regularlj' and gradually enlarging from 

 the apex; transverse section circular. Living-chamber cylindrical, well 

 developed, having a length about three times the diameter of the tube at 

 the last septum, and without any marked constriction or expansion 

 toward the aperture; air-chambers regular, having a depth of five mm. 

 where the diameter of the tube is nine mm., and of eight mm. where the 

 diameter is twenty mm. Septa apparently smooth and thin, the margins 

 sometimes slightly thickened, and with a concavity equal to an arc of 

 about 110° ; sutures straight, and somewhat oblique in a dorso-ventral 

 direction; siphuncle lai'ge, eccentric, less than one- third the diameter of 

 the tube from the ventral walls, with a diameter of two mm. where the 

 tube measures twenty mm. in diameter, and diminishing but slightly 

 toward the apex. Test and surface markings not preserved ; internal 

 mold smooth with the exception of a low, longitudinal ventral carina. 

 This species is distinguished from 0. exile by the carina on the internal 

 mold, the comparatively deeper air-chambers, and the more eccentric 

 position of the siphuncle; it also closely approaches 0. emaceratum in 

 several features, but the septa are a little more frequent. 



The specimens in the Maryland Collection referred to this species are 

 broken and not very satisfactory for identification; but one shows five 

 air-chambers or camerae each of which has a depth of five mm. and 

 another large internal impression of a living chamber shows in the sep- 

 tum at its base the siphuncle which is very eccentric, considerably more 

 so than it is represented in the figure of 0. exile and agreeing with that 

 of 0. tclamon.'^ These specimens were submitted to Dr. J. M. Clarke 

 who wrote as follows concerning them : " These specimens have rather 

 deeper camerae and a more cylindrical body chamber than 0. exile, in 

 these respects approaching more nearly 0. telamon H." 



Occurrence. — Eomney Formation, Hamilton Member. Robinsons 

 Farm 2 miles south of Patterson Depot, W. Ya. 



Collection. — Maryland Geological Survey. 



" PaL N. Y., vol. v, pt. ii, pL 85, figs. 2 and 4. 



