PRODUCTUS. 173 



difference, however, from our specimens is that the ribs may be rather more 

 numerous, and that the interruptions extend to the marginal parts ; and it 

 appears to me most probable that they both belong to the same species, and 

 therefore that Mr. Hennah's specimen is a Devonian fossil. 



The figure of Producta laciniata, M'Coy, 1 from the Middle Carboniferous of 

 Ireland, which is very like the figure given by Sowerby of his species, but has 

 much finer and more spinous ribs, is regarded by Davidson as possibly a variety 

 of P. fimbriatus, though separated from it by M'Coy. 



5. Productus corrugatus, M'Coy. Plate XXI, figs. 4, 5. 



1844. Producta corrugata, M'Coy. Synops. Carb. Foss. Ireland, p. 107, pi. xx, 



fig. 13. 



1845. Productus tenuistriatus, Verneuil. Pal. Russia, vol. ii, p. 266, pi. xvi, 



fig. 6. 

 1855. Producta coruugata, M'Coy. Brit. Pal. Foss., p. 459. 

 1861. Peoductus cora, Davidson (? not d'Orbigny). Brit. Foss. Brach., vol. ii, 



pt. 5, p. 148, pi. xxxvi, fig. 4 ; and pi. xlii, 



fig. 9. 

 1896. — tenuistriatus, Whidborne. Proc. Geol. Assoc, vol. xiv, p. 376. 



Description. — Ventral valve large, subglobose, rounded or perhaps sometimes 

 slightly depressed along the centre of the back. Ears small and undefined. 

 Beak wide, convex, incurved, overhanging the hinge-line, and having a few strong 

 foldings or rounded wrinklings on its sides and on the ears. Ribs extremely 

 numerous, minute, rounded, irregularly flexuous, sometimes alternating, divided 

 by similar furrows, and very occasionally bearing minute spines ; remaining of a 

 uniform size over the whole valve, and sometimes splitting into two or three and 

 again reuniting. Surface crossed by close, regular, microscopic transverse strice. 



Localities. — In the Porter Collection are nine or ten specimens from Pre- 

 mington and one from Kingdon's Shirwell; in Miss Partridge's Collection is one 

 from Fremington. 



Size. — The specimens are all crushed or imperfect; one is 38 mm. long by 

 25 mm. wide; others were evidently larger. 



Remarks. — Our shells are rounded or perhaps sometimes flattened on the 

 back, but I have not seen anything in them that amounts to a sinus. The ribs, 

 though always minute, seem to vary in size and number in different specimens, as 

 also do their flexuosity and their habit of division and reunion, which are some- 



- 1814, M'Coy, 'Synops. Carb. Foss. Irel.,' p. 110, pi. xx, fig. 12. 



