BRACHIOPODA. 
279 
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 Davidsonia and Lept^enisca, 
have been observed by Dr. Davidson. 
Shell-substance strongly punctate. 
Type, Leptcena rugosa, Dalman = Produda rugosa, His- 
inger —Conchites rhomboidalis, Wilckens. Upper Silurian. 
Observations. Having already given at some length the reasons for restricting 
the application of the term Strophomena, Rafinesque, as defined and illustrated 
by de Blainville, the genus Lept^na, 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. multirugata, 
McCoy” (Permian Fossils, p. 104). All these are of the type of L. rhom¬ 
boidalis. 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 Leptcena four species, in the following order: 
L. rugosa , Hisinger, L. depressa, Sowerby, L. euglypha, 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 1/69. The other two 
species are not congeneric with L. rhomboidalis. Davidson, however, regarding 
the first three as proper Strophomenas (1853-1884), decided to take the last 
species, L. transversalis, as the type of Leptcena, 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. euglypha, a member of 
the genus Strophonella, Hall, 1879, would have to stand as the type of Lep- 
Fig. 18. Leptcena rhomboidalis, 
showing impressions of spiral arms. 
After Davidson. 
