BRACHIOPODA. 



279 



Fig. 18. LrptiFiiti rhomhoUlnlUt 

 re-ssioiisorsj)!! 

 I'V r>.v\'ii>soN". 



.septum, and the anterior pair of scars is frequently obliterated by prominent 

 callosities. At the line of geniculation the interior sur- 

 face is elevated into a very prominent, sharp, or abruptly 

 rounded crest. Spiral callosities for the support of the 

 brachia, similar to those in Daviusonia and LeptvENIsca, 

 have been observed by Dr. Davidson. 



Shell-substance strongly punctate. 



Type, Leptana rugosa, Balmnn = Producia rugosa, His- .„„wi„ffinM.re,ssionsor»,>,™uum. 

 mger=Conchites rhomboidalis, Wilckens. Upper Silurian. 



Observations. Having already given at some length the reasons tor restricting 

 the application of the term Strophomena, Rafinesque, as defined and illustrated 

 by DE Blainville, the genus Lept^ena, of Dalman, will be left to rest upon its 

 first and typical species, Produda rugosa, Hisinger. This is precisely the interpre- 

 tation of the genus followed by most authors from 1830 to 1860 Prof. King, 

 in the Annals and Magazine of Natural History, 1846, and in his Monograph 

 of the Permian Fossils of England, 1850, proposed restricting the genus more 

 narrowly than heretofore, including only "such shells as L. analoga, Phill., L. 

 semiovalis, McCoy, L. plicotis, McCoy, L. nodulosa, Phill., and L. muUirugata, 

 McCoy" (Permian Fossils, p. 104). All these are of the type of L. rhnm- 

 bnidalis. During the early part of this period Strophomena, as already pointed 

 out in the discussion of that genus, was a term of uncertain value. 



Dalman placed under his genus Lept^na four species, in the following order: 

 L. rugosa, Hisinger, L. depressa, Sowerby, L. eughjpha, Dalman, L. transversalis, 

 Wahlenberg. The same author observed that the first two of these had been 

 included by Wahlenberg, in 1821, under the name Anomites rhomboidalis, this 

 specific term having been first used by Wilckens, in 1V69. The other two 

 species are not congeneric with L. rhomboidalis. Davidson, however, regarding 

 the first three as proper Strophoinenas (1853-1884), decided to take the last 

 species, L. transversalis, as the type of Lept^na, and it is this use of the term 

 that has become current among palaeontologists. Were it necessary, however, 

 to reject the first two of Dalman's species, the third, L. eughjpha, a member of 

 the genus Strophonella, Hall, 1879, would have to stand as the type of Lep- 



