BDRNF, : SODTH AFRICAN APLYSIIDJ^. 



53 



The beak is strongly incurved, and upwardly reflexed. The sinus is 

 deeply excavated, and extends barely a third the length of the shell. 

 The colour of the shell is yellowish, owing to the strong periostracum 

 which extends from 1 to 2-5 mm. beyond the anterior border of the 

 calcified part 



Alimentary canal : The jaws, which have an elongated quadrilateral 

 shape, are lateral brush-like developments of a continuous delicate 

 sheet of chitin that encircles the buccal cavity just inside the mouth. 

 They are covered with slender, rod -like, chitinous processes (Fig. 4), 

 about -2 mm. in length, tliat slightly swell distally, and terminate in 

 a rounded end. 



The radula is of the type common to the family, with a formula of 

 28 : 1 : 2.S, the outer lateral teeth being, as usual, more or less 

 rudimentary. The median tootli is broad and has three cusps, a 

 median which is irregularly denticulate along its edge, and on either 

 side a smaller smootli cusp. The first lateral has one large smooth 

 cusp; the other teeth, except those quite at the side, have a large 

 internal denticulate cusp, and lateral to it a smaller smooth cusp. 



The buccal mass is nearly globular (9 mm. long by 8 mm. broad). 

 The oesophagus measures 9 by 2 mm., and is longitudinallj' pleated 

 internally. It leads into a voluminous crop measuring roughly 

 30 by 12 ram., and making one complete spiral twist to the right 

 before opening into the muscular gizzard. This latter region is, as 

 usual, very clearly defined externally by the abrupt anterior and posterior 

 margins of the thick layer of circular muscle fibres of which its w^alls 

 are composed. Internally it is armed with two or three irregular 

 rows of pyramidal horny teeth of different sizes. The gizzard passes 

 without constiiction into the stomach, which in turn gradually narrows 

 to form the intestine. Two large bile ducts and a narrow caecum 

 open into the intestinal end of the stomach. 



The arrangement of the gut-coils, a character that seems to differ 

 in different species, resembles very closely that figured for T. leporina 

 in Bronn's Thieneich, Bd. iii, Abth. 2, pi. Ixv, fig. 7. The salivary 

 glands and hepato- pancreas call for no remark. 



The opaline gland is of very large size, and is composed of long 

 transparent conical lobules, which measure about 1 mm. in diameter 

 at their outer ends, and gradually narrow towards a common duct 

 that opens by a large aperture, as stated previously. 



The nervous system has the form normally present in the genus. 



The gill and heart are also of the normal type. The first portion 

 of the aorta is provided with a leaf-like enlargement {crista aortm) 

 closely attached to the anterior wall of the pericardium. The aorta 

 occupies the central line of this enlargement, and on either side is 

 a wing-like expansion. 



The reproductive organs are in no way specially remarkable, but it 

 may be mentioned that the hermaphrodite gland, -which is buried as 

 usual in the right side of the apex of the visceral mass, is rounded, 

 and the albumen gland is small and sausage-shaped. Otherwise they 

 very closely resemble the published figures of European species such 

 as T. leporina. 



