BITTIUM PINGUE. 67 



a Ghemnitzia by the author, but it belongs to the vetusta-groxrp of Cerithium, as 

 defined by Hudleston — a group not elsewhere recognised in the beds above the 

 Great Oolite. 



Genus BITTIUM, Leach. 



The genus Bittium is often ([noted as Leach's, bnt it appears that Leach never 

 published anything upon the subject, only naming certain shells in his own 

 cabinet by this name. After his death the MS. prepared by him was published 

 by Gray in 1847 ('Ann. Nat. Hist.,' vol. xx, p. 2(57), the already named species 

 included in it being indicated, but no description was given. Zittel ('Handbuch 

 der Palreontologie '), and Fischer (' Man. Conch.,' p. 680) give the definition thus : 

 " Shell small, lengthened, with numerous granular whorls, irregularly varicose ; 

 anterior canal short, scarcely distinct, not curved ; lip open, varicose and dilated 

 on side, columella edge simple." It is certain that many Jurassic shells show these 

 characters rather than those of a Cerithium with its curved canal. 



Bittium pingue, sp. now Plate VII, fig. 10. 



Type. — The lower half of the shell preserved, in which are five whorls; the 

 greatest breadth along the spirals of the large whorl is 7 mm. The sutures make 

 an angle of 79° with the axis, but are impressed lines only. It is ornamented by 

 five rows of small equal knobs, joined longitudinally by a broader, and spirally by 

 a narrower rising. The longitudinal groups — of which there are twenty-four in 

 the last whorl — are curved in a direction concave to the aperture. The base is 

 convex, joining the side without an angle. It has seven spiral ridges not divided 

 into knobs. The columella is nearly straight, making an angle, or pseudo-furrow, 

 with the outer lip. The left lip smooths over the spirals of the outside of the whorl. 



Distribution ami lulu/ions. — From Scarborough, in the Museum of Practical 

 Geology. There is a second example of the species in the York Museum, but 

 it is not known elsewhere. One of these is the foundation for the record of 

 G. gemmatum, but it is not that species, which is not recorded by Hudleston 

 from the Cornbrash. It differs in the presence of spiral bands between the knobs 

 and the undivided spirals on the base. The last feature also divides it from 

 G. millepunctatum (Desk) of the Oxfordian, which it otherwise much resembles. 



