6 INTRODUCTION. 



from the imperforate valve," torn, cit., 1833, p. 161, pi. xxii, fig. 6, Ter. chilensis,) near 

 the middle line, and close to the hinder margin of the dorso-pallial lobe, are the short, 

 approximate tendinous insertions of the adductor brevis, ^, and the line of attachment of 

 the almost tendinous cardinales muscles, «'. 



The exterior surface of the ventral lobe, when exposed with the same care, shows the 

 two pairs of pallial sinuses and ramified generative lobes. The muscular extremities 

 perforating this lobe are more aggregated than in the opposite lobe : the anterior, forming 

 a pair, of a pyriform shape, with the great end forwards, belong to the adductor brevis, 

 ((, fig. 2, p. 9, (" anterior pair of muscles arising from the perforate valve," tom. cit., 

 1833, p. 161, pi. xxii, fig. 5, Ter. chilensis): external and posterior to these is a 

 second pair of muscular attachments belonging to the ' retractor inferior,' ib. $', (" posterior 

 pair of muscles of the perforate valve," tom. cit., 1833, p. 162, pi. xxii, fig. 5;) in the 

 median interspace of the foregoing muscles is the common attached extremity of the 

 adductores longi, ib. d : of a pyriform figure, with the great end backwards, and emar- 

 ginate or notched at the middle from the lodgment of the anal end of the intestine, ib. 4^. 

 Immediately behind this part are the ends of the small pair of cardinales muscles, ib. ?«', 

 and behind these the transversely extended glistening surface of attachment of the 

 rausculo-aponeurotic fibres of the sheath of the peduncle {capsularis r') ■ 



As in the Terebratulce described in my former Memoir, the pallial lobes, with the 

 exception of the small part at the hinge of the shell, are free in the rest of their circum- 

 ference, and inclose a wide cavity to which the sea-Avater is admitted, and in which float 

 freely the long filaments of the fringed arms. The long adductors and expanded origins 

 of the short adductors appear also to cross the pallial cavity, but they are inclosed by a 

 delicate transparent duplicature of the pallial membrane : a similar duplicature invests the 

 beginning of the oesophagus, and is bent around the terminal part of the intestine, 

 being reflected upwards a little above the vent, which opens, like the mouth, into the 

 pallial interspace, immediately behind the ventral insertion of the long adductors. The 

 visceral mass, consisting of the alimentary canal, pi. i, fig. 1, r,^,y^, liver, w, hearts, i, 

 and looped origins of the ventral ovaria or testes, pi. iii, fig. 1, 12, occupies the small space 

 between the long adductors, 0, p, the hinge, and the peduncle. 



MUSCULAR SYSTEM. 



I have but little to add to the illustrations of this system derived from the dis- 

 sections of Ter. chilensis, Ter. Sowerbii, and Ter. psiftacea, in my former Memoir ; 

 but figures are subjoined to render its anatomy better understood. Taking the 

 ventral or perforated valve, to which the peduncle is directly attached, as the more fixed 

 point, the adductores longi (PI. i, fig. 2, 0, p,) arise from a single pyriform area at the 

 middle of that valve, v, a little behind a line transversely bisecting it ; the fibres soon become 

 tendinous, converge, and group themselves into two lateral muscles forming a pair ; each 

 of these muscles as it approaches the opposite valve expands and subdivides into an 



