44 BRITISH PERMIAN BRACHIOPODA. 



description to be specifically distinct from St. Goldfussi; and Baron Schanroth informs 

 me that he is also of opinion that, although Strophalosia Lewisiana and St. Goldfussi 

 are closely related, the first can always be distinguished by its more circular shape, as well 

 as bv its lower and smaller area. Messrs. Howse and Kirkby, on the contrary, state that, 

 after the careful study of this form, they cannot find one fixed character by which to 

 distinguish the shell we are now describing ; that the two extreme forms I represent 

 (PI. Ill, figs. 3 and 19 — 22) graduate by almost imperceptible degrees into each other, 

 having in the regular form a narrow area and incurved beak, and in the other a larger 

 area and a depressed beak. I have therefore considered the shell under description as a 

 variety of Goldfussi, with the denomination of Lewisiana, so that it may be thus retained, 

 or specifically separated, should such a course be considered desirable. 1 



In a paper published in the ' Annals of Natural History ' for March rsnd April, 1856, 

 Professor King has proposed to consider the shell (fig. 23 of our PL III) as a variety of 

 Strophalosia excavata, to which he has applied the varietal term Width' i/ensis, but from 

 such imperfect and insufficient material as the cast of a single dorsal valve, we can decide 

 with but little certainty; it may or not belong to Stroph, Goldfussi or its var. Lewisiana. 



The variety Lewisiana has been found in the same beds and localities already recorded 

 for Stroph. Goldfussi, both in this country as well as on the Continent, but is not so 

 abundant as the typical form of Minister's species. 



Strophalosia lamellosa, Geiniiz. Plate III, figs. 24 — 41. 



Orthotrix lamellosus, Geinits. Versteinerungen, p. 14, pi. v, figs. 16 — 26, April, 



1848. 



Strephalosia Morrisiana, King. Catalogue of the Organic Remains of the Permian 



Rocks of Northumberland and Durham, p. 9, 19th of 

 August, 1848 ; Monograph of English Permian Fossils, 

 p. 99, pi. xii, figs. 18—25, and 27—32; Annals and 

 Mag. of Nat. Hist , vol. xvii, 2d series, March and April, 

 1846. 



Leptjena cancrini, M'Coy. British Palaeozoic Fossils, p. 457, 1 8 /) r> (not Productiix 



Cancrini, Verneuil and Keyserling). 



1 It has been argued that the regular form of a shell should be taken as the type of the species, and 

 not the irregular growth, and I quite coincide in the opinion ; but when we view a species under its general 

 aspect, and find that the great majority of individuals of which it is composed are not perfectly regular, 

 the beak being more often twisted a little to the one side or to the other, and that the shell is more often 

 sub-trigonal, and rarely circular as in Stroph. Goldfussi, with or without a slight mesial elevation in the 

 smaller valve, and corresponding depression or sinus in the opposite one, we feel bound to select our typical 

 shape from the normal condition, or the one that gives the best representation of the general character of 

 the species, and not only from one particularly favoured individual who may have been perfectly symmetri- 

 cal in all its parts. 



