GASTEROPODA. 19 



round and hollow, and that the upper part of them had been decorticated, and a portion 

 consisting of the two sides of the original ribs only left, the effect of which would be 

 to show a number of thin sharp, instead of half that number of wide and blunt costae. 

 The apex is sharp, the three first volutions being without riblets, and the fourth volu- 

 tion has 4 or 5 rounded riblets, beyond which these riblets are double in number. My 

 specimen is not sufficiently perfect to show if there have been any spiral striae. The outer 

 lip is much curved and there is a large deep sinus a little below the suture ; the outer 

 lip is also sharp, without any striae or ridges on the inside of it. My specimen re- 

 sembles the figures given by M. Nyst with the name of Pleurot. acuticosta (' Coq. foss. 

 de Belg.,' p. 529, pi. 42, fig. 5), but that figure is indifferent, and the description 

 is too short to supply the deficiency. Pleurot. incrassata from Touraine somewhat 

 resembles our shell, but I have not a specimen for comparison. The above name is 

 given provisionally. 



PLEUROTOMA ICENORUM, S. Wood. 2nd Sup., Tab. Ill, fig. 8, a, 6. 



PLEUROTOMA ICENORTJM, & Wood. 1st Supplement Crag Moll., p. 35. 



Locality. Cor. Crag near Orford. 



There is so much doubt and difficulty about this shell that I find it necessary to give 

 another figure of it, from a perfect specimen in my own cabinet. My shell has a row of 

 nodules formed at the projecting portion of the outer lip, with a row of smaller nodules 

 adjoining the suture ; thus making two rows on all but the lower volution. The two 

 apical whorls are quite smooth and without ornament, making the apex very obtuse ; 

 differing thereby from the representation of PL coronata of Bellardi. At the base 

 there is an umbilicus caused by a slight obliquity of the volutions outwardly. Two 

 specimens have been sent to me from Dr. Reed's collection with the name of PL uinbili- 

 cata, A. Bell, which correspond with Icenorum. Our shell has unfortunately had several 

 names. In Mr. Prestwich's list, p. 145, it is called Pleurotoma galerita^ Phil. In Mr. 

 BelPs List of the English Crags, p. 35, it is said to have been figured and named by 

 Dr. von Konen as PL Hosiusii (' Mioc. Nord. Deutch. Moll.,' p. 105, taf. 2, fig. 12 a, d). 

 These foreign species appear to me (judging from representations) to be different from 

 our shell, which has an obtuse apex and an umbilicus, neither of which is possessed by 

 them. The name of PL semicolon , given in Crag Moll., is also erroneous for the reasons 

 mentioned in my first Supplement, p. 35. I would have adopted Mr. Bell's name of 

 umbilicata, were it not that the shell to which I had previously assigned the name 

 Icenorum is, in my opinion, the same species. 



