180 



PTEROPODA. 



ated on the right side of the neck beneath the 

 corresponding lateral fin : the liver is of no 

 great bulk, and forms a nearly globular mass. 



The organs of generation consist of an 

 ovary which occupies the greater portion of 

 the right side ; of an oviduct of moderate 

 length ; of a testicle which is almost as large 

 as the ovary, and of a common deferent canal. 

 The penis is here, as in Clio, an organ al- 

 together distinct from the testicle : it is situ- 

 ated, as already said, beneath the oesophagus, 

 where it is folded upon itself; and when pro- 

 truded, issues through an orifice placed in the 

 front of the neck and a little below the mouth. 

 Tt is represented in situ in Jig. 1 1 -i. 7, and 

 detached in 8. 



The brain (/. 114. 7, r) is large, flat, 

 and of a square form, slightly narrowed pos- 

 teriorly : the nerves issue principally from its 

 angles, two of them going to join a double 

 ganglion situated beneath the oesophagus. 



The salivary glands appear to be wanting. 



PNEUMODKRMA. Another genus of the 

 Pteropod Mollusca, anatomized by Cuvier, 

 embraces the Pneitmoderma, which presents 

 many peculiarities of structure, more es- 

 pecially as relates to the position of the re- 

 spiratory organs and the tentacula placed at 

 the sides of the mouth and other anatomical 

 details, so that it will require to be described 

 at length. In this genus, the body is without 

 a shell, having two fins situated on the sides 

 of the neck, but is distinguished by having two 

 bunches of tentacula in the vicinity of the 

 mouth, and by carrying its branchial organs at 

 the surface of its body near its posterior ex- 

 tremity. 



The body of this mollusk is of an oval 

 shape (Jig- S 15. 1, a), the head (6) is round, 



Fig. 115. (I to 9). 



3. The same placed with the head downwards, 

 and seen from the right side to show the branchiae. 



4. The same enlarged and shown in the position 

 of Jig. 1. The skin is divided and turned aside to 

 show the muscular envelope of the viscera and the 

 pericardium in situ. 



5. The same, the muscular envelope and perito- 

 neum laid open to show the viscera in situ. 



6. The same, with the viscera developed. 



7. The same : the organs of generation are turned 

 aside ; the stomach laid open and the integuments 

 of the head divided to show the mouth and its ap- 

 purtenances. 



Anatomy of Pneumoderma. (After Cuvier.) 



1. Pneumoderma, natural size, anterior aspect. 

 ^. ihe same, posterior aspect. 



8. The mass of the mouth detached and opened 

 longitudinally to show its interior. 



9. Interior of the head after the removal of the 

 oral organs, showing the penis and the inferior 

 ganglia in situ. 



The same letters answer to all the figures. 



a, body ; b, head ; c, mouth ; d, lips ; e, their 

 fleshy appendage ; f, tins ; g, branchias ; //, branchial 

 vein ; i, auricle of heart ; k, pericardium ; / /, mus- 

 cular envelope of viscera ; m, liver ; n, testicle ; o, 

 ovary ; p, stomach laid open ; q, rectum ; r, r, fleshy 

 appendages to oral cavity ; s, tongue ; t, it, anterior 

 membranous compartment of mouth ; t, t, t, oral 

 tubercles ; c, c, tentacles ; v, salivary glands ; x, their 

 dilated ducts ; y, brain ; z, smaller mucous ganglia ; 

 a., penis ; /}, opening of common generative canal, 



