CLASSIFICATION OF THE BRACHIOPODA. 



107 



cussions that have taken place on this subject,^ a few observations, however, may be 

 admissible. No author seems to have as yet discovered substantial characters by 

 which the shells placed in Strophomena or Leptcena can be generically divided ; those 

 hitherto proposed, as justly observed by Professor M'Coy; " do not seem worthy of generic 

 rank." 



After a careful examination of a great number of species I agreed, with Mr. Salter, to 

 maintain both Strophomena and Leptcena subject to certain limitations, but we could not 

 prefix to this last many very important distinctive characters. Strophomena would 

 include all species agreeing with S. planumhona, alternata, yrandis, Jilosa, euglypha, 

 funiculata, antiquata, pecten, expansa, depressa, &c. Lept^na we would typify by such 

 forms as L. transversalis, sericea, transversa^ ohlonga, Davidsoni, tenuicincta, &c. These 

 two genera thus formed are well distinguished by habit, but the distinctive characters 

 rest chiefly on the form of the muscular impressions and cardinal process. 



Professor King, on the other hand, is desh'ous of dividing the above-named shells 

 into three sections or genera, observing that the external and internal characters of 

 L. alternata, depressa, and transversa, or transversalis, are sufficiently distinct to admit of 

 the names Strophomena, Leptana, and Plectamhonites,^ being advantageously applied : 

 thus he proposes to typify the first by S. alternata. " Valves regularly plano-convex ; fora- 

 luen, when existing, partly edged by the deltidium, pallial vessels running at once almost 

 direct, or in a somewhat radiate mariner from the muscular impressions to the front'' (see 

 PI. VIII, fig. 160). Leptcena, he typifies by L. depressa, Dal.; ''Valves geniculated, 

 wrinkled; umbone of the dental valve 

 foraminated ; pallial vessels run- 

 ning parallel with each other till 

 they have reached to near the anterior 

 region, where they sioeep round sub- 

 marginally on both sides, giving off 

 a series of sfnaller vessels." But the 

 learned Professor admits into his sec- 

 tion Strophomena, shells essentially geniculated, such as S. euglypha and imbrex; and the 



1 Refer to Professor M'Coy's Synopsis of the Carb. Limest. Fossils of Ireland, p. 104, &c., 1844 ; and 

 Brit. Pal. Foss. in the Woodw. Mus., p. 232, 1852. — Professor King's paper on the Palliobranchiata, ' Ann. 

 and Mag. of Nat. Hist.,' vol. xviii, p. 36, 1846 ; and the same author's Monog. of English Permian Fossils, 

 p. 103, &c., 1849. — Mr. Salter's Palseontological Appendix, in the 'Memoirs of the Geol. Survey of Gr. 

 Britain,' vol. ii, pt. 1, p. 377, 1847. — Mr. Sharpe ; Quart. Journal of the Geol. Soc, vol. iv, p. 1/8, 1848. — 

 M. d'Orbigny; Pal. Fr. Ter. Craaces, vol. iv, p. 335, 1847; and Prodrome, vol. i, 1849.— De Verneuil ; 

 Bull, de la Soc. Geol. de France, vol. v. May, 1848, &c. 



2 This section was proposed by Pander, in his work entitled 'Beitriige zur Geognosie des Russischen 

 Reiches,' 1830, his types being P . j)Ianissima, transversa, lata, imbrex, ohlonga, &c., figured in his pi. xix. 



^ These figures are reductions from those published in Professor King's ' Monograph of the Permian 

 Fossils of England,' pi. xx, figs. 6, 7. 



Fig. 37. 



Fig. 38. 



Strophomena analoga? 



Interior of the ventral and dorsal valves. 



a, ovarian spaces. e, foramen. t, teeth. 



