MR. R. OWEN ON THE ANATOMY OF THE BRACHIOPODA. 147 
that gallant and scientific officer Commander James C. Ross, R.N.!, I find that the 
situation of the ova in dried specimens when the mantle-lobes adhere to the shell, would 
be such as Cuvier has described. 
It is from the above-mentioned materials that the following account of the anatomy 
of Terebratula has been derived. 
On separating and removing the valves of Terebratula, the soft parts of the animal 
appear as in Figg. 5., 6., 14. & 15. Plate XXII. The arms and viscera, as in Lingula, 
are inclosed between the lobes of the mantle, which are precisely adapted to the inner 
surface of their corresponding valves, and are in such close contact with them as to 
require great care in separating the valves from them. That lobe of the mantle which 
corresponds to the perforated valve, is traversed longitudinally by four large vessels? ; 
the opposite lobe is similarly traversed by two such vessels. These appearances were 
constant in the four specimens examined. 
' The margins of the mantle are thickened, as is commonly observed in the Lamelli- 
branchiate Bivalves ; but which in this case results less from contraction than from a 
peculiar structure, presently to be described. In Lingula and Orbicula the same margins 
are distinctly and beautifully ciliate ; but in Terebratula the marginal cilia are so minute, 
as only to be perceptible by means of a lens. 
At the posterior part of each of the lobes the expanded fleshy extremities of the 
muscles are seen ; those which were attached to the perforated valve being nearer the 
hinge by their whole length, than the anterior pair of the opposite valve. Each of the 
oval muscular disks is composed of an anterior larger muscle, and a posterior smaller 
one. Through the transparent mantle may also be seen the green-coloured follicular 
liver intervening between and surrounding the muscles, and the folded ciliate arms. 
As the visceral mass occupies but a small space near the hinge, the lobes of the 
mantle can be reflected to a greater extent than in Lingula. On examining in this 
way the inner surface of the lobes of the mantle, another important difference between 
Terebratula and Lingula is perceived. In the latter genus the branchie consist, as 
described by Cuvier, of narrow elongated vascular productions, which are attached to 
the inner surface of the lobes of the mantle; whereas in Terebratula there only appear 
the venous trunks above mentioned. These vessels I first perceived in Mr. Cuming’s 
small specimen, where they were sufficiently conspicuous from the outside of the 
mantle, owing to their being distended with coagulated blood; but on the inner side 
they are more distinctly seen, commencing by numerous branches from the margins 
of the pallial lobes, from the union of which, at about two lines distance from the 
‘ This gentleman, having learned from my friend Mr. Broderip that J was engaged in the investigation of the 
anatomy of Terebratula, submitted for my examination, in the most liberal manner, the largest of the few 
specimens which the untoward circumstances attending the late perilous expedition permitted him to bring 
safely to this country. It was fished up from adepth of twenty-two fathoms near Felix Harbour, in lat. 70°N. 
on the east side of Boothia Peninsula. 
2m. m. Figg. 5. 7. 3m. m. Figg. 6. 8. 
VOL. I. x 
