CLASSIFICATION OF THE BRACHIOPODA. 



119 



Fig. 42. 



merable produced tubercles protruding often in the shape of short spines, especially visible 

 near the marginal portions of the shell ; no calcified supports for the arms, which were 

 probably small and vertically coiled. 



Obs. Although much has been published on this extensive genus by several learned 

 Palaeontologists, authors do not seem to coincide in the interpretation to be given to some 

 of the impressions observable on its internal surface. Professor King has endeavoured to 

 restore the muscular system ; but from an attentive examination of the identical specimens 

 on which the learned Professor conducted his examinations, as well as others in the 

 Cambridge University Museum, the cabinet of Mr. Tate, &c., neither Mr. Woodward nor 

 myself were able to recognise in a 

 distinct manner more than the scars 

 left by the cardinal and adductor 

 muscle,^ as seen in the annexed 

 woodcut. A variety of opinions have 

 been expressed, as to the manner in 

 which the animal of this genus lived; 

 some believe that the shell was affixed 

 by its spines, others by the extre- 

 mity of the beak of larger valve, 

 or suspended by muscular fibres 

 issuing from the margins of the 

 valve !^ M. d'Orbigny supposes that 

 the animal lived lying on soft bot- 

 toms, with its smaller valve upper- 

 most, in a similar manner to Oysters, 

 Scallops, and Sjiondt/lus striatus, in 

 which the lamellae and spines served to retain the animal in a fixed position ; but 

 M. de Koninck objects that these spines are often so long and so delicate, as to 

 make one believe they would be fractured under such conditions. The remarkable 

 tubular expansion of the larger valve in Prod, proboscideiis led the last-named author 

 to suppose that out of its extremity passed the muscular fibres of attachment; 

 M. d'Orbigny, on the contrary, states it to be his belief that the prolongation 

 was due to malformation produced by accidental circumstances, connected with the 

 supposed constrained position in which the animal lived, having forced the mantle to 



Terehratula, and agrees with Crania in three important particulars, viz. the absence of a hinge, the simplicity 

 of the vascular impressions, and the shifting of the processes for the attachment of the arms, from the hinge- 

 margin to the centre of the shell. 



' Professor King states that he found impressions of pedicle muscles, and indeed that he was able to 

 trace all the muscular scars observable in Terebratula. ('A Monograph of English Permian Fossils.') 



2 See Geinitz' 'Deutsch. Zechst./ t. vi, f. 1. 



Fig. 41. Fig. 43. 



Productus giganteus (from Mr. Woodward's drawings). 



Fig. 40. Interior of dorsal valve. — 41. Interior of ventral valve, with the 

 umbo removed. — 42. Ideal section of both valves. — 43. Hinge-line of 

 dorsal valve : j, cardinal process; a, adductor; r, cardinal muscles ; 

 s, hollows occupied by spiral arms ; v, reniform impressions ; b, bra- 

 chial processes } ; h, hinge-area. 



