56 FAUNA OF THE CORNBRASH. 



the characters of the species very well. Its diameter is 138 mm. ; the transverse 

 diameter is '82 of this, the last whorl *58, the thickness *24. The side has a 

 peculiar inflated appearance, owing to the rounded infundibular form of the 

 umbilicus and the greatest thickness being some way (3- out) from it. The 

 periphery is somewhat produced radially. Up to a whorl breadth of 43 mm. the 

 peripheral portion has the relics of sigmoid radial ribs, just as in C. discus; beyond 

 this point nothing appears upon the cast. The sutures are most characteristic. 

 They may be described as consisting of 12 narrow-pointed lobes, or backwardly 

 directed teeth, whose axes or edges are all more or less parallel to the curve of the 

 periphery. The eleven saddles, or forward parts of the sutures, are more or less 

 incised, but usually only slightly so. The outer eight of them do not all advance 

 to the same level, but hang back in the centre, thus producing the appearance of 

 a " superior lateral lobe," the sides of which are more jagged than any other part 

 of the suture-line, and form between them, with the intervening shorter saddle, 

 the " three teeth " mentioned in the type. 



These peculiarities are continued to the smaller part of the whorl, and are 

 quite distinct from the features of G. discus of the same size, as seen by comparing 

 Fig. 3 and Fig. 2, though the sutures, as a whole, both show a Clydonian type. 



Distribution. — Besides this specimen from Norton Brize and that recorded 

 from Chippenham by Oppel, there are at least two from Bedford and a fragment 

 from S. Cerny, recognisable by their sutures and shape, and probably one from 

 Hoi well of smaller size (64 mm.), in which the sutures are not so well developed. 



Clydoniceras ptychophorum (Neumayr). Plate VI, fig. 3. 



1869. Ammonites discus, Brauns, Der Mittlere Jura, pi. 2, fig. 4 (non fig. 1). 



1871. Harpoceras ptychophorum, Neumayr, Ceph. v. Baliu, Al>h. k k. Geol. Eeiclisanst., vol. v, p. 27. 



Type. — Brauns, figuring a species as Am. discus, says of it that it has flat, 

 broad ribs, which correspond each to 6 — 8 fine ones, which bend sharply forwards 

 to pass over the periphery. The diameter is 33 mm., the thickness is 8 mm., and 

 the height of the last whorl is 17 mm. The umbilicus has a breadth of 6 mm. 

 This at first grows with the outside of the shell, then remains stationary, and later 

 becomes narrower. The sculpture is lost with age, and three quarters of the last 

 whorl is body chamber. From Lechstedt, in Macroc&phdlus beds. Neumayr (loc. 

 cit.) calls the species thus defined Harpoceras ptychophorum, thereby making it the 

 type. The sutures are drawn in Brauns' figure, though not mentioned. They 

 consist in an undulating line which sinks in the centre and there terminates in 

 a point directed backwards. 



Description. — If this be a distinct species, which seems by no means certain, 



