BY II. LEIGHTON KESTEVEN. 713 



If the whole of the embryonic life is spent as a pelagic exist- 

 ence, the wide distribution of this species is easily explicable. 



Tritonium spengleri, Chem. 



(Plate xxxvi., figs. 8-9.) 



Apex thin, semi-pellucid, corneous, shining, consisting of four 

 and one-half whorls, covered with a thin brown epidermis, very 

 finely transversely and longitudinally lirulate. Junction of 

 embryo and adult marked by a broad flat varix and a complete 

 change of structure. Dimensions of protoconch (approximately), 

 length 3, breadth 2 mm. 



The peculiar oblique way in which the apex is set on the adult 

 whorls is unique. The above dimensions are taken from the 

 specimen figured. 



Tritonium speciosum, Angas. 

 (Plate xxxvi., figs. 10-11.) 



Apex solid, slightly polished, dull yellowish-brown, consisting 

 of a little more than one whorl, sculptured with fine revolving 

 hair-lines, which are broken up into irregular lengths. The 

 junction between embryonic and adult structure is marked by a 

 small varix and a complete change of structure. Dimensions of 

 specimen figured, length 3'5, breadth 1-5 mm. 



Gyrineum AUSTRALASIA, Perry. 



(Plate xxxvi., fig. 1.) 



Ranella leucostoma, Lam. [vide Mr. Hedley's Note on this 

 synonymy, mite, p. 631). 



Apex solid, polished; colour variable, of difterent shades of 

 brown; consisting of about five whorls, perfectly smooth and 

 devoid of an epidermis. The junction, between embryo and adult 

 is marked by the sudden acquisition of a complex sculpture. 

 Dimensions of protoconch (approximately), length 5-3, breadth 

 4 mm. 



Although this apex has a thoroughly strong appearance, it is 

 generally dropped early in the life of the adult mollusc, half 

 47 



