LAMELLIBRANCHIATA. 127 



Larger pyriform crypts, measuring G — 8 mm. deep are also 

 occasionally found, some of them in fossil wood, and these probably 

 belong to the Pholas constricta of Phillips. 



Another and larger species is evidenced by a series of fine 

 clavate crypts in the paddle-bone of a Pliosaurus, which measure 

 4 inches in depth, 1 inch in diameter. Their courses are some- 

 what tortuous. I have found similar great burrows in the Hythe 

 beds of Hythe, Kent. 



One very curious organism, probably of the same nature, was 

 found at Upware : — a pyriform shelly structure, with small circular 

 opening, is continued below into an irregular swollen tube, which, 

 in one specimen, turns sharply upwards and, uniting with a fellow 

 tube, ends in a large, slightly expanded, irregular common opening. 

 Altogether the specimen has much resemblance to a Scotch 

 bagpipe. 



Pholas (Fistulana) constricta, Phillips. 



Pholas constricta, Phillips, Geol. Yorkshire, pi. n., f. 17. 

 Roemer, Nordd. Kreide, pi. X., f. 11. 



Localities. Upware, Speeton. 



LlTHODOMUS PHOSPHATICUS, sp. 110 V. 



(Plate vii., fig. 1, a, b.) 



A small, rather variable boring shell, abundantly found in 

 crypts in the phosphatised casts of Ammonites, &c. 



Description. Shell small, cylindrical, the surface smooth or 

 marked only by lines of growth. Umbones nearly terminal, broad, 

 flattened, and incurved. Two gentle shoulder ridges start from 

 the umbo, the one more obtuse, running to the anterior pallial 

 margin, and the other, which is angular in front, passing obliquely 

 to the posterior end ; a slight sinus is therefore formed in the 

 pallial border. 



The casts shew a posterior ligament groove, bordered by ridges. 



Measurements. Length, 7 mm. ; breadth, 3 mm. ; thickness 

 (through both valves) 3 mm. 



Localities. Upware, Potton, Brickhill. 



