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BRITISH DEVONIAN BRACHIOPODA. 



Pkoductus subacoleatus, Schnurr, iu v. Meyer and Dunker's Palseontograpbica, Band 



ii, p. 228, pi. xliii, fig. 4 «• 1853. 



— Davidson. Quarterly Journ. of the Geol. Soc, p. 33G, 



pi. xv, fig. 12, 1853. 



— — Steininger. Geogn. Beschreibung der Eifel, p. 86, 1853. 



— — Sandberger. Dei Brach. Rheinischen Schichtensystems in 



Nassau, p. 75, pi. xxxiv, fig. 17, 1855. 



Spec. Char. Shell sub-hemispherical, transversely semicircular, sometimes as broad 

 as long; hinge-line straight, usually about equal to, or a little less than the width of the 

 shell. Ventral valve pretty regularly vaulted and very gibbous, without sinus; beak small, 

 prominent, and incurved, but overlying very slightly the hinge-line ; ears small, gradually 

 flattened ; hinge-area linear, with a small fissure in the middle. Dorsal valve very concave, 

 following closely the curves of the opposite one. Surface of the ventral valve marked with 

 numerous concentric lines or wrinkles of growth, as well as with irregularly scattered 

 projecting tubercles, or cylindrical, curved, hollow spines. These spines are very irregu- 

 larly scattered over the surface of the valve, and appear at greater or lesser intervals from 

 each other; they are also more numerous on the ears. Surface of dorsal valve marked 

 with concentric lines and wrinkles on the auriculate portions of the valve ; small circular 

 pits exist likewise, here and there, over its surface. Proportions variable — 

 Length 18, width 21 lines. 

 11 „ 11 „ 



Obs. This is a common and well-known Devonian fossil, named subaculeatus, by Sir 

 R. Murchison, on the 6th of April, 1840, and fragaria, by Sowerby, on the 30th of May 

 of the same year, and it is much to be regretted that Sir R. Murchison had not submitted 

 to Mr. Sowerby the specimens he had collected at Ferques, since that gentleman was at 

 the time describing for Sir Roderick those he had picked up in beds of a similar age in 

 Devonshire. Had this been done, a number of synonyms and a certain amount of con- 

 fusion in the nomenclature would have been avoided. 1 



Sir R. Murchison remarks that his Productus subaculeatus approaches nearly to 

 Martin's Productus (Anomites) aculeatus, but that it differs from that species by the 

 manner in which the spines rise from the surface of the valve, those in the Devonian form 

 being stated to rise perpendicularly to the surface of the valve. Prof. M'Coy has likewise 

 observed that the elongation of the tubercles in Sovverby's figures were produced by 

 mechanical compression in the rock, the part of the specimen not crushed having them 

 round. It is, bow r ever, very difficult to procure from our Devonian rocks uninjured spe- 

 cimens, with the shell itself well preserved, but I was able to obtain the communication of 



1 From having unfortunately overlooked the fact of Murchison's paper in the ' Bulletin ' having been 

 read twenty-three or twenty-four days sooner than that of Sowerby, published in the 'Transactions of the 

 Geol. Soc.,' I adopted at p. 23 of this Monograph the term Spirifer disjunctus, Sow., while that of 

 Sp. Verneuilli has a claim to priority. 



