174 DEVONIAN FAUNA. 



times excessive. Davidson's figures show still finer and more numerous ribs than 

 do our shells. 



Our shells are so exceedingly like M'Coy's P. corrugatus from the Yellow 

 Sandstone and Carboniferous Limestone of Ireland as to be certainly identical with 

 it; for, though M'Coy says it had no spines, his figure seems to show indications of 

 minute rare spines such as are evident in our specimens. Davidson, following 

 de Koninck, who had examined d'Orbigny's types, united M'Coy's species with 

 the South American P. Cora, d'Orbigny. On the other hand, d'Orbigny's original 

 figure of P. Cora 1 looks totally different. Its spines are much coarser and more 

 frequent, and it has a row of large hinge-spines. Waagen, who figures an Indian 

 example which bears out at least the first two of these distinctions, sides with 

 M'Coy in denying its identity with the English, Irish, and Belgian shell. He 

 divides his section Lineata into two groups : (1) those with a sinus, as 

 P. Neffidievi, Verneuil 2 (which Davidson united to P. Cora), and P. lineatus, 

 Waagen ; 3 and (2) those without a sinus, as P. Cora, d'Orbigny, and ? P. 

 semireticulatus, Martin. Again, Tschernyschew distinguishes the Permio- Carbo- 

 niferous P. tenuistriatus, Verneuil, from P. corrugatus, M'Coy (which M'Coy 

 had united with it), by the irregularity of the fission and reunion of the ribs, and 

 both these forms from P. Cora, d'Orbigny, by the absence of spines on the middle 

 parts of the shell, and by the fineness of the ribs. But our Devonshire 

 specimens are accurately identical with P. tenuistriatus in every respect, and in 

 some of them the irregularity and flexuosity of the ribs and the paucity of the spines 

 are fully as great as in the Russian shell which Tschernyschew figures, while in 

 others the ribs seem as straight and the spines as imperceptible as described by 

 M'Coy. 



It seems, therefore, best to place our shells with P. corrugatus and P. tenui- 

 striatus, which they prove to be mutually identical, and to leave the disputed 

 question of the identity of P. Cora, d'Orbigny, in abeyance. 



6. Productus, cf. P. subaculeatqs, Murchisoii. Plate XXI, figs. 1 — 3. 



Localities. — Two fragmentary specimens from Fremington and one from 

 Pilton are in the Porter Collection. One from Saunton is in the Barnstaple 

 Athenaeum. 



Size. — Width about 30 mm. Length of a spine more than 44 mm. 



1 1842, d'Orbigny, ' Paleont. Voyage Atner. Merid.,' p. 55, pi. v, figs. 8—10. 



2 1845, Murchison, Verneuil, and Keyserling, ' Kussia,' vol. ii, p. 259, pi. xviii, fig. 2. 



3 1884, Waagen, ' Salt Range Brack,' p. 673, pi. lxvi, figs. 1, 2 ; and pi. lxvii, fig. 3. 



