712 PROTOCONCHS OF CERTAIN PORT JACKSON GASTEROPODA, 



Tritonium pusiforme, Kiener. 



(Plate XXXV., figs. 3-5.) 



Frotoconch ovoid, umbilicate, thin, semi-pellucid, shining, 

 corneous, light brown, variously marked with spots or stripes of 

 darker colour, consisting of about three whorls, covered with a 

 very thin light brown epidermis. Transversely sculptured with 

 very line growth-lines; the epidermis supplies four ciliated ridges 

 which encircle the last whorl, the top one of which is continued 

 on the earlier whorls. Mouth nearly ovoid; outer lip thin, well 

 rounded, and very slightly reflected; inner lip undefined; pillar 

 short, slightly bent. Anterior canal merely indicated by a broad 

 shallow sinus. Umbilicus small, and owing to the transparency 

 of the shell only seen in certain lights. The transition from 

 embryo to adult is marked by a very slight reflection of the outer 

 lip of the embryo and the complete change of the shell-structure. 

 Dimensions of protoconch, length 2, breadth 1*9 mm. 



Tritonium olearium, Linn. 

 (Plate XXXV., figs. 4-5.) 



Protoconch thin, attenuately conical, imperforate, semi-pellucid, 

 shining, corneous, light brown, consisting of six whorls, under 

 the microscope very finely transversely and longitudinally lirulate, 

 covered with a very thin, light brown epidermis. Mouth some- 

 what ovate; outer lip thin, rounded; inner lip distinct; pillar 

 slightly bent back anteriorly. Anterior canal distinct under the 

 pillar but undefined on the outer lip. The junction of the 

 embrj^onic with the adult structure is marked by a slight varix and 

 a complete change of structure. A few coarser transverse lines 

 may be noticed on the body whorl of the embryo just before its 

 junction with the adult. Dimensions of protoconch, length 4-3, 

 breadth 2*5 mm. 



The general appearance of this protoconch is that of an Alaba^ 

 and but for the anterior canal might be mistaken for one. It 

 looks peculiarly out of place standing up from the rather flat 

 crown of the early adult whorls. 



