8 SYNOPSIS OF THE CHARACTERS OF THE 



at the larger end, and only four lines at the smaller ; the septa are about two lines distant from each other, 

 rather more at the large end, and about half a line less at the small end. 



Orthoceeas steinhaijeri. Sow. 



Orthocera Steinhaueri. Sow. Min. Con Orthoceras Steinhaueri. P/iil. Geol. York. 



Sp. Ch. — Shell very gradually tapering ; section circular ; septa about one and a half lines distant ; very 

 convex, simple ; siphon lateral ; surface strongly striated transversely. 



This species is principally distinguished by the distance and great convexity of its septa. Usually about 

 quarter of an inch in diameter ; tapers one line in an inch. 



Orthoceras striatum. Sow. 



Orthocera striata. Sow. Min. Con. 



The O. striatum described by Sowcrby, in the Mineral Conchology from the Cork limestone, is stated 

 to be striated longitudinally . Professor Fleming, in copying Mr. Sowerby's characters into his work on British 

 Animals, alters it to transvei'se stria3, specimens agreeing with this latter description are common in the Cork 

 limestone, and I at first thought, with Professor Fleming, that they might be the true O. striatum. Mr. 

 Sowerby, however, mentions, in the Sil. System, that the O. striatum differs from the O.Jilosum (which has 

 sharp, longitudinal ridges), in the fineness of its stria;. I have, however, seen no specimen corresponding with 

 the original description in this particular, nor does Mr. Sowerby's figure afford any information. 



Orthoceras sulcatulum. M'Goy. (PI. I. fig. 4.) 



Sp. Ch. — Gradually tapering, conic ; section slightly elliptical ; septa one-fifth the diameter, distant from 

 each other ; surface with coarse, waving, unequal transverse striffi. 



This species closely resembles Professor Phillips' figure of the O. chictum, Sow., but differs from his 

 description in the coarseness of the transverse sulci (which also distinguishes the surface from O. subjlexuosum, 

 Miinst.) From Sowerby's original figure and description of his O. cinctum it differs entirely, that species being 

 nearly cyHndrical, and with very fine, direct, transverse striae, while the present shell has very coarse, waving, 

 unequal ridges, and tapers more rapidly in form ; specimens of the true O. cinctum, with those characters, are 

 not uncommon ; the present species is very rare. A specimen, two inches long, and one inch six lines in dia- 

 meter at the base ; taj)ers five Hnes. 



Orthoceras (Loxoceras) Breynii. Mart. sp. 



Orthoceratites Breynii. Alart. Pet. Derb Orthocera Breynii. Sow. Min. Con. 



Sp. Ch. — Shell tapering ; section elliptical ; siphuncle in one focus, at the raised edge of the septa ; 

 septa very oblique, numerous ; very slightly concave. 



This species has the septa remarkably oblique, and what is very unusual, they are nearly flat ; a specimen 

 two inches and eight lines long, and one inch three lines at base, tapers four lines ; the septa are from one and 

 a half to twO' lines apart. 



Othoceras (Loxoceras) distans. M'Coy. (PI. IV. fig- 1) 



Sp. Ch. — Tapering five hnes in two inches ; section elliptical ; septa concave, one-half their lesser dia- 

 meter distant from each other, obHque in the direction of the shorter diameter of the shell, with a broad, shal- 

 low wave in the side ; siphimcle nearly central. 



