﻿212 BRITISH FOSSIL CEPHALOPODA. 



•backward-curving lines ; on the inner whorls there are about 40 gently backward- 

 curving feeble ribs. The surface is also covered by very fine riblets, 11 per line, 

 and by transverse epidermids in some specimens. The body-chamber has a slight 

 tendency to leave the coiled portion, and reaches on the average about } of a 

 whorl. The inner side of the aperture is slightly produced, and the middle has a 

 forward curve, and in some there is a slight constriction there. The septa are 

 from 20 to 34 per whorl ; fewer at first, but increasing in number continually ; not 

 very convex in the suture, but curving forward very rapidly both inside and outside, 

 making almost a funnel-shaped lobe at the former place. The siphuncle is not 

 accurately determined in any, but one example had some indications of an internal 

 siphuncle, but in another it looks more probably central. 



Relations. — The great proportionate breadth of the outer whorl distinguishes this 

 from N. bohemicus. It is quite symmetrical, and is therefore not a Trochoceras, 

 though its young form might have some resemblance to T. comu-arietis. 



Distribution. — In the Lower Ludlow rocks at Stokesay (4) and Ledbury (10). 



Nautilus quadrans, Blake, PL XXX. fig. 1. 



Type. — The rate of increase is 1.7, and last whorl .36 of the diameter. There is 

 no sign of asymmetry. The section is subquadrate, rounded on the front, rather 

 flat on the sides, and rounding gently on the inner side. The body-chamber is 

 slightly produced beyond the curved part. Ratio of thickness to breadth as 9 to 10. 

 On the earlier whorls there are backward-curving ribs with parallel riblets ; these 

 die off and leave the outer whorl smooth till near the aperture, where there are 

 backward-curving undulations. The aperture has a very prominent and rounded 

 inner edge, produced beyond the rest. The septa are about 50 per whorl; their 

 convexity is slight in a transverse direction. No siphuncle is seen. The whole is 

 covered with transverse epidermids. Diameter about 3 inches. From the Lower 

 Ludlow, Ledbury. In the collection of Dr. Grindrod. 



General Description. — The other specimens agree in the general dimensions 

 and the shape of the section with the type. The whorls are always just in contact ; 

 there is no sign in any of asymmetry, but the last chamber leaves the whorls for 

 1^ inches in one specimen. The septa may be as many as 60 per whorl, and are 

 moderately concave. The siphuncle appears to be sub-central and moderate in size. 

 The outer whorls are always smooth, except for backward lines of growth, but the 

 inner ones when seen have feeble backward-curving numerous ribs. Most specimens 

 are crowded with transverse epidermids. 



Relations. — If this be truly & Nautilus, it differs from N. bohemicus in its more 

 open whorls, and its more quadrate section. There is no elongated straight portion 



