ANATOMY OF THE TEREBRATULA. 5 



To the question proposed to me by their discoverer, " Can they have any analogy to 

 the hepatic papillae of the Nudibranchiates ?" I could only reply that, the pallial lobes are 

 so distinct from the visceral mass, as compared with the skin of the Nudibranchiates, that 

 they cannot have any special functional relation to the liver. And, in regard to the 

 generative system, the membranous tubes penetrating the shell-pores in the Terehratula 

 jlavescens are so much more minute than the ova discernible in the ramified ovaria, 

 and their presence is so equally manifested over the non-ovarian and ovarian parts of the 

 mantle — the same remark being equally appKcable to the pallial lobes and ramified 

 testes in the male — that one cannot connect them, as subordinately related in function, 

 with the generative organs. 



The difficulty of satisfactorily assigning the final cause or purpose of the microscopic 

 pallial processes is increased, as in many analogous cases, by the non-development of the organs 

 in question in certain Brachiopoda, e. g., the recent Atrypa and the fossil Bhi/nconellida, 

 which latter, from the general analogy of the structure of their shell, might be supposed 

 to have the respiratory organs at the same low degree of development as the Terebratulida, 

 and to have the same need for the minute calcifying or excretory ciliated shell-tubes. 



Owing to this organic connection between the pallial lobes and the shell, which is 

 particularly close towards the periphery of the lobes, I have been compelled, in some of 

 my dissections, to sacrifice the shell, and remove it piecemeal, in order to preserve and 

 show the characters of the external lobes of the mantle entire. The difficulty of removing 

 the imperforate valve is increased by the median crest, d, fig. 1, p. 9, and the attachments 

 of the loop, ih., e e, both of which require to be broken close off from the imperforate 

 valve, and left inclosed in the folds of the mantle that invest them, in order to obviate 

 laceration of its outer surface. 



The dorsal lobe, d 2h of the mantle, thus exposed in the Terebratula Jlavescens, shows 

 the single pair of wide pallial sinuses, 5, containing the correspondingly ramified testes or 

 ovarium, according to the sex ; the sinuses and their contents extending from the outer side 

 of the hepatic portion of the visceral mass, forwards, along the outside of the great 

 anterior muscular impressions, to near the anterior border of the mantle : the sinus is 

 equidistant from the median line and the lateral border of the mantle, in each half of the 

 lobe : the marginal ramifications of the sinus, the large sheathed cilia, and the smaller 

 marginal cilia, correspond in structure with the same parts in Ter. chilensis} Immediately 

 behind a line equally bisecting transversely the mantle lobe in question, are the expanded 

 extremities of attachment of the two divisions, o' /, fig. 1, p. 9, of the adductor long us muscle, 

 ("anterior pair of muscles arising from the imperforate valve," tom. cit., 1833, p. IGl, 

 pi. xxii, fig. 6, Ter. chilensis.) 



In the space behind these muscles, and between them and the retractores superiores, 

 the two lateral masses of hepatic cseca are clearly visible beneath the thin transparent 

 pallial covering. Behind the retractores superiores, (" posterior pairs of muscles arising 



1 Trans. Zool. Soc, pp. 147, 148, pi. xxii, fig. 11. 



