J, Starkie Gardner — Eocene Aporrhdidce. 



533 



The ribs are prominent, slightly curved, and occupy a space of about 

 1 mm. each. The stria3 are faint or invisible. The body- whorl is 

 slightly angulated, and the ribs break up suddenly into 3 rows of 

 round tubercles, the upper of which is the more prominent. The 

 wing is relatively small, attached to the body and the penultimate 

 whorls only, and with one digit. The canal is very short. 



The species is strictly confined to the Thanet Beds at Heme Bay, 

 and the wing is rarely preserved. Hence Professor Morris was led 

 to regard it as a Scalaria, though he noticed that the last whorl was 

 carinated, and the ribs broken upon it. — Quart. Journ. Geol. Soc. 

 1852, p. 266,. 



ApoRRHAis FiRjiA, sp. nov. Brockenhukst. Plate XVn. Figs. 1 & 2. 



This comes next in point of size to the larger Oldhaven species, 

 measuring 40 mm. in length, by at least 32 across the wing. The 

 spire is very blunt, the whorls much wider than high and tumid. 

 The ribs are curved, oblique, strongly marked, fine, but becoming 

 coarser towards the last whorl, and breaking into three rows of 

 nodes on the body-whorl, the upper being far more prominent and 

 rounded than the rest ; the strise are inconspicuous. The body- 

 whorl is more angulated than usual. The wing is short, and is pro- 

 duced into two digits more equal than in the previous species, and 

 is continued to the apex of the spire. The canal is long. 



This is a rare shell at Brockenhurst, only a few specimens being 

 preserved in the Edwards' collection in the British Museum. 



A small fusiform shell from Hempstead bears the label AporrJia'is 

 in the same collection, but it possesses none of the characteristics of 

 even the immature shells of the genus. 



The study of this Family, limited to its Eocene range, does not 

 carry us far. It will be noticed, however, that the oldest or Thanet 

 Bed species is more like a Cretaceous form, and less like the living 

 than any other, and that the newest or Oligocene form from 

 Brockenhurst approaches in all its characters the most nearly to 

 the late Tertiary A. pes-felecani, in which the ribbed spire has 

 finally given place to a tuberculated and angular one. The gap in 

 succession is also remarkable, for while the genus abounds in all the 

 marine beds of the Lower Eocene, it is wholly wanting in the 

 Bracklesham, and even the Barton series, and only reappears in the 

 Oligocene of Brockenhurst. A precisely similar gap occurs in 

 Belgium. It seems clear that during the Eocene period it belonged 

 to the northern sea, and was absent in parts at least of the southern. 



The following Table shows the Range of 

 Great Britain. 



the Eocene Aporrhdidce in 





Thanet 

 Beds. 



Oldliaven 

 Beds. 



London 

 Clay 



Bagshot Headon Bembridge 

 Series. Series. Series. 



A. Bowerbanlcii 



A. Margerini 

 A. triangulata 

 A. Soiverbii 

 A. labellata 

 A.Jirma 



X 



X 

 X 



X 

 X 





S 





