TEREBRATULA. 
Puate I, 
Genus TEREBRATULA, Lhwyd. 
Testa inequivalvis, equilateralis, globosa vel ovata, interdum 
depressiuscula, nunc levigata, nunc radiatim striata 
aut costata, semper punctata, valvd supernd ventralt, 
tumido-converd, posticé rostraté et perforatd, fora- 
mine interdum integro, deltidio clauso, interdum im- 
perfecto, deltidio plus minus partito, valvd infernd 
dorsali, plerumque planiore ; cardine processibus denti- 
formibus varie callosis in valvd ventrali composito, 
processibus alteris in valvud dorsali valide wterclau- 
dentibus; valvd dorsali ad cardinem lobatd, apophyse 
internad varid munita. 
Shell inequivalve, equilateral, globose or ovate, sometimes 
rather depressed, now smooth, now radiately striated 
or ribbed, always*punctured, upper valve ventral, tu- 
midly convex, beaked and perforated posteriorly, per- 
foration sometimes entire, with a closed deltidium, 
sometimes made imperfect by a more or less divided 
deltidium, lower valve dorsal, generally flatter; hinge 
composed of two variously callous tooth-like pro- 
cesses in the dorsal valve, strongly interlocking with 
two other processes in the opposite valve; dorsal 
valve lobed at the hinge and furnished with a vari- 
able internal apophysis. 
Forty years ago, when M. Valenciennes prepared for 
Lamarck, who was already blind, the monograph of this 
genus for his ‘ Histoire des Animaux sans Vertébres,’ the 
shells of only twelve to fourteen species of recent Tere- 
bratule had been observed, the soft parts of only one, and 
the organization of the Brachiopods generally was only very 
imperfectly known. Although Linnzus had remarked that 
the animal of 7. caput-serpentis differs not less from any 
other animal that he had found im shells, than night from 
day,—‘animal quod intus conditur 4 vermibus qui aliis 
in conchis omnibus sibi invicem fere sunt similes non dif- 
fert minus quam 4 nocte dies,’—the Zerebratule and its 
allies were still arranged with the lamellibranchiate Con- 
chifera. 
De Blainville, and subsequently, by a more elaborate in- 
vestigation, Professor Owen, ascertained that the branchize 
do not exist in the form of lamelle, but are incorporated 
bya system of vessels with the mantle-lobes. Along with 
the discovery of the phenomenon that the mantle-lobes of 
the Brachiopods perform not only the office of secreting the 
shell, but also of respiration, another peculiarity was ob- 
served, namely, that the valves are differently placed from 
those of other bivalves, with regard to the position of the 
animal,—that, in fact, they are not side-valves connected 
dorsally by a cartilage and ligament, but dorsal and ventral 
valves connected, in the Teredratule, by closely interlock- 
ing tooth-like processes in relation with an internal apo- 
physary skeleton, and a complicated system of muscles, to 
which may be added a force acquired through the habit of 
the animal in affixing itself to foreign bodies by a fibrous 
byssus-like tendon. Another peculiarity which presented 
itself was the presence of a pair of internal ciliated arms ; 
and the Brachiopods, even as late as 1830, were arranged 
by Cuvier and his contemporaries in immediate proximity 
to the Cirrhipedes. It had, however, been observed that 
the ciliated arms of the Brachiopod, are quite distinct 
organs from the cirrhi of the Cirrhipede, and Professor 
Owen’s beautifully detailed exposition of its anatomy re- 
moved all doubt on the subject. Projecting from the 
mouth of the animal on either side, they correspond, or, to 
speak scientifically, are homologous with, the labial palps of 
other bivalves, prolonged, as it were, on muscular tuhes 
so as to require being folded or coiled up. In Terebratula 
an internal bony skeleton or apophysis is formed, proceed- 
ing from the hinge in connection with the dorsal valve, 
for the support of the arms, and being extremely variable 
in structure, it affords excellent characters to the concho- 
logist for the distinction of groups. 
The Zerebratule are chiefly deep-dwelling Brachiopods, 
and from the few pains given to dredging them from their 
native haunts, the varieties of the apophysary skeleton 
were not until lately known. The dredgings of M. Gau- 
dichaud, M. D’Orbigny, MM. Quoy and Gaimard, Capt. 
King, Mr. Cuming, Capt. Belcher, Professor Forbes, Mr. 
MacAndrew, Mr. Barlee, and others, have furnished spe- 
cimens with internal skeletons, coupled with valuable ba- 
thymetrical observations ; and the different forms of apo- 
physis, and corresponding development of the arms, have 
been well observed by M. D’Orbigny, Mr. Davidson, Mr. 
Woodward, and Mr. King. Excellent systematic cata- 
logues of both recent and fossil species have been published 
by Mr. Davidson, and by Dr. Gray, assisted by Mr. Wood- 
ward, in which the different forms of apophysis are em- 
ployed as the grounds of subdivision, and the geographical 
distribution of the species in space, in depth, and in time 
has been worked out with much ingenuity by Professor 
Suess. 
February, 1861. 
