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 that of Lingula, 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 Trimerella. 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 Dinobolus 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, progressed pari passu with the assumption of Trimerelloid 
characters. 
Genus LAKH MIN A, CEhlert* 1887. 
1885. Davidsonella, Waagen. Mem. Geol. Surv. India; Palseontologialndica, Ser.XIII, I,iv, fasc.5, p.762. 
Not Davidsonella, Munier-Chalmas, 1880. Bull. Societe Geologique de France. 
1887. Lakhmina, CEhlert. Fischer’s Manuel d£ Conchyliologie ; Brachiopodes, p. 1265. 
This genus is defined by Dr. Waagen in essentially the following terms: 
General outline more or less linguloid. 
The ventral valve is the larger and 
possesses a prominent apex, which is 
provided, on its lower surface, with a 
deep furrow for the pedicle. In the in¬ 
terior of the ventral valve, the cardinal 
margin is somewhat thickened, without 
Davidsonella ( — Lalchmina ) linguloides , after Waagen. 
forming a distinct area. Below this fig. is. Pcdicie-vaive. fig. m. Brachial valve. 
* In the preparation of the discussion of this genus, and g-enerally throughout the volume, the term 
Davidsonella had been adopted, not being aware that the name had been used by Munier-Chalmas in 1880 
for a genus of Liassic brachiopods allied to Thecidium. We are therefore reluctantly compelled to adopt the 
term Lakhmina, proposed by CEhlert ; though it must not be forgotten-that- it is to Dr. Waagen we are 
indebted for the careful analysis of the genus. 
