28 



PALAEONTOLOGY OF NEW YORK. 



. termined, but we have evidence that the outer or epidermal layer is more 

 largely corneous than those within, and, so far at least, its structure is in 

 harmony with tliat of Li.ncula, as demonstrated by Gratiolet. But on the 

 other hand, the relative amount of mineral matter in the shell is far in excess 

 of that in Lingula, and its structure in this respect is wholly in consonance with 

 the other features which establish- its transitional position in the line of de- 

 velopment from Lingula to Tkimeiiella. In the latter genus and its associates, 

 the heavy shells have been rarely preserved, or when preserved, their original 

 structure is so essentially altered by dolomitization and crystallization, that it is 

 impossible to gain an accurate conception of their composition. Undoubtedly 

 they were substantially calcareous, with small percentages of organic matter, the 

 latter perhaps relatively increased in the thinner-shelled forms,like D[N0B0lus and 

 some species of Monomerella. The evidence at hand would lead to the presump- 

 tion that the loss of the organic constituents of the shell, and the increase 

 in calcareous matter, progresaed pari pass2i with the assumption of Trimerelloid 

 characters. 



Genus L A K H M I N A , (Ehlert.* 1887. 



1885. Dandsonf.llti,\{ ji.K<iKi!. Mem. Geol. Surv. IniUa ; P.al.'ecMitulogia liidica, Ser.XIlI, I.iv, fast-.O, p. 762. 



Not Datndxonella, MrNiKR-CnALMAs, ISSO. Bull. Socieb' Gfologi<iue de France. 

 1S87. Lakhmina. (Khi.kht. l''i.-<c-hi'i-V Manuel de Cdnchyliologie ; Brachiopcides, p. 12C5. 



Tins genus is defined by Dr. Waagen in essentially the following terms: 

 General outline more or less linguloid. 

 The ventral valve is tlie larger and 

 possesses a prominent apex, which is 

 provided, on its lower surface, with a 

 deep furrow for the pedicle. In tlie in- 

 terior of the ventral valve, the cardinal 

 margin is somewhat thickened, without 



„ . ]• • 1, , >>i'ri<J^onena[=Lalhmimi)linriuloUles, a.tlevW\A.GKii. 



lorming a distinct area. Below this F"g l^l- I'ediolcvalve. fig. U. Brachial valvc. 



^ 111 llie i,iei.aialiuii ul' the discussiuu v( iliis yeiiu-s and g-eiierally tliioiigli,Mit the vnUune, the term 

 Davidso.nblla had I.een adi.pted, not lieing awaie that the name h.id been u.sed liy Munier-Chalmas in 1880 

 for a genus of Li.assie brachiopods allied to Thbcidium. We are therefoi-e reluctantly compelled to adopt the 

 term Lakhmina. proposed by CRhlert ; though it must not be forgotten that it is to Dr. Waagen we are 

 in<lel)t<'d for the careful analysis of the genus. 



