PRODUCTUS. 33 



localities. Some British examples have measured 7 lines in length, 5^ in width, and 4 in 

 depth, but is commonly a smaller shell ; while a few foreign specimens have exceeded the 

 dimensions above given. 



The genus, or rather sub-genus, to which this interesting species should be referred 

 has been the subject of considerable difference in opinion. Schlotheim placed it among 

 his Terebratulites ; J. de C. Sowerby made it his Spirifer minutus ; Brongniart con- 

 sidered it to be a Terebratula ; Von Buch named it Orthis Laspii ; and Professor King 

 created for its reception a new genus, Streptorhynchus. In 1853 I left it provisionally 

 with Orthesina; and Professor M'Coy places the shell in Leptcena (1855). Thus, 

 since 1816, this little species has been located into six different genera by different 

 authors ! 



The fortunate discovery of several perfect detached valves by Messrs. Howse and 

 Kirkby has enabled me to furnish some additional figures, which will serve to complete 

 our knowledge of its internal characters. 



Mr. Howse and Professor King state to have obtained the shell from the shell lime- 

 stone of Tunstall and Humbleton hills, Dalton-le-Dale, Silksworth, Ryhope-field House, 

 and in the Breccia of Tynemouth Cliff. In Germany Dr. Geinitz, Von Buch, Decken, 

 and Professor Quenstedt mention it from the Lower Zechstein of Ropsen, Corbusen, and 

 Schmerback, as well as from the Zechstein conglomerate of Konitz and Altenstein. Baron 

 Schauroth describes the shell from Possneck, and M. De Verneuil mentions having found 

 it at Bielagorskaia. 



Family— PRODUCTION. 



Genus — Phoductus, Sowerby. 



(Introduction, Vol. I, p. 117, 1853.) 



Productus horridus, J". Sowerby. Plate IV, figs. 13 — 26. (King's Mon., pi. ix, 



figs. 29—31 ; and pi. xi, figs. 1—13.) 



Productus horridus, Sowerby. Min. Con., vol. iv, p. 17, pi. 319, fig. 1, Jan., 1822 

 = Prod, clava, Sow., Min. Con., pi. 560, figs. 2 — 6. 



This well-known and characteristic fossil has been often described and illustrated. 1 



1 De Koninck, ' Recherches sur les Animaux fossiles de la Belgique,' and ' Monographie du Genre 

 Productus,' p. 158, pi. xv, fig. 1, &c, 1847. Geinitz, ' Versteinerungen,' p. 15, pi. vi, figs. 1 — 14, 1848. 

 King, 'A Monograph of the Permian Fossils of England,' p. 87, 1850. M'Coy, 'British Palaeozoic Fossils,' 



5 



