MACROCEPHALITBS HUDLESTONI. 47 



In the figured specimen in the Museum of Practical Geology (No. 32 in 

 Table I, No. 8650) the umbilicus cannot be called vertical, bul the sigmoida! 

 curvature is very well shown, so probably it is misshapen. The specimen from 

 " Northants " (No. 33 of Table J), very likely from Thrapston, is much 

 thinner in proportion. In fact, we scarcely know sufficient of this species. This 

 is especially seen to be the case as the types arc neither of them obtained from a 

 known bed of Cornbrash, and also from the fact that the smaller of them is also 

 the smallest of all that are referred to this species. 



Distribution. — Besides the types other specimens have occurred from Scar- 

 borough (4), Cayton Bay (1), Appleby (1), Lincolnshire (1), Bedford (1), Northants 

 (2), and Peterborough (3). This, therefore, like M. macrocephalus, is confined, so 

 far as actually known, except the smaller type, to the northern part of the range. 



Macrocephalites hudlestoni, sp. nov. Plate IV, fig. 3. 



Type. — Only the body chamber preserved. The thickness is somewhat more 

 than half the diameter. Compressed on the sides, umbilicus one fourth the 

 diameter, edge rounded, marked with the ribs, which are not very sharp, but 

 narrow and distinct. They have scarcely any bend, but run out obliquely in a 

 forward direction in relation to the radius. The intercalated ribs arise at less than 

 one third out — all are equal on the periphery — and those that join to form an 

 umbilical rib scarcely make the rib larger when joined. Those on opposite sides 

 generally join again after splitting over the periphery. 



Numerical characters are given in No. 11 of Table I. The shell appears to 

 have been excessively thin, to judge by a Bryozoan growth. From Rnshden, in the 

 Collection of Mr. W. H. Hudleston. 



Description. — A smaller specimen from Ailsworth (No. 3 of Table 1) shows the 

 same characters, except that the umbilicus is somewhat smaller. Another specimen 

 from Peterborough is half enclosed in a later whorl, which is septate up to a 

 diameter of 5 inches, and has fourteen very convex septa, the sutures being very 

 approximate and more complicated. They cannot be drawn in either case. The 

 ribs bend forward near the periphery. This is the largest specimen including the 

 outer whorl. The thickness is generally about half the diameter, which suggests a 

 relation to M. typicus, but the latter loses its thickness more rapidly towards the 

 umbilicus, and thus presents a different aspect, while the ribbing is different in 

 many respects. 



Distribution.— Specimens have occurred at Rushden (1), Appleby (I s ). Ailsworth 

 (1), Peterborough (2), and possibly at Thrapston (1) and Scarborough (1). 



Besides the above-named species of Macrocephalites, which are characterised by 



