466 PAL2E0ST0L0GY OF NEW YORK. 



curve to the bottom of the acute outer lateral lobe, the distance is equal to 

 the depth of two and a half to three and a half air-chambers, measured in 

 their greatest depth. The ventral lobe is short, penetrating the adjacent 

 air-chamber about 2.5 mm., where the entire depth is nine mm. The suture- 

 lines are strongly impressed upon the interior cast, and in a simply exfoliated 

 specimen are comparatively very wide, from the thickening of the septa at 

 their margins. 



The siphuncle is small, cylindrical, and placed close beneath the shell, on 

 the peripheral margin. 



The test is known only upon a single individual, and has a thickness of 

 about one - mm. at the base of the chamber of habitation. The surface is 

 imperfectly preserved, showing somewhat lamellose, transverse stride, with 

 faint indications of other markings. The sinus, inferring from the direction 

 of the striae, has been narrow and shallow. 



The internal cast is essentially smooth, preserving the septal margins or 

 impressed suture-lines, with impressions of the fine surface stria?. A speci- 

 men, of which a cast in iron pyrites is preserved, measures about forty-five 

 mm. in its greatest diameter; another well-marked individual of the species 

 has had a diameter at least twice as great ; and another large individual, 

 referred to this species, has a lateral diameter of about ninety-five mm., and, 

 measured from the outer margin of the grand chamber across the centre, has 

 a width of more than 110 min. 



In its smaller forms this species has much general resemblance to G. simula- 

 tor, in which the volutions are more rotund, and the periphery broader. In 

 the septate character there is also a considerable general resemblance between 

 the two forms. In G. simulator, however, the inner lateral lobe is very shal- 

 low, the lateral saddle less elevated, and the exterior lateral lobe much less 

 extended and less acute. These differences are well shown on comparing 

 figures 1 and 2 of plate 69 with figures 1 and 2 of plate 72, where the speci- 

 mens are of nearly the same size. In older individuals of G. Patersoni the 

 differences are more strongly marked, as may be seen in figures 3 and 4 of 

 plate 72. When occurring in the same rock and in similar conditions of 



