88 COLLECTIONS FROM MELANESIA. 



mouth and for a short distance along the sides, and then simple and 

 gradually increasing in the width of the expansion towards the 

 end, where it is very wide beneath Ihe branchia; it is stained with 

 black on the inside of the edge. Branchial plume posterior, concealed 

 between the foot and the hinder lobes of the doi'sal disk. Head 

 presenting exteriorly a small lobe on each side the oral opening. 



Shell internal, situated at the hinder extremity above the branchia, 

 white, calcareous, uncoiled, consisting of one or two volutions, 

 thickened at the free " sutural line," convex externally and concave 

 within, cup-shaped at t he commencement, with the outer edge 

 extended by a broadish membranous expansion. 



Total length 33 millim. ; cephalic disk 18 long and 10 wide at 

 the broadest part ; shell with a greatest diameter of 8 millim., and 

 about 2 in height. 



I lab. Thursday Island, Torres Straits, 4-5 fathoms, on a sandy 

 bottom. 



The only species which appears to have been recorded from the 

 Australian coasts is Aglaia lin olata, figured by H. & A. Adams in 

 the ' Genera of Recent Mollusca,' vol. iii. pi. 58. tig. 4. This differs, 

 however, in the form of the anterior dorsal disk and its small 

 size in proportion to the hind part of the animal, in addition to 

 which the colour and markings appear to be quite distinct. Aglaia 

 gigliolii, from Japan, described by Tapparone-Canefri ( Voy. Magenta, 

 p. 110, pi. l.fig. 18), may be distinguished by the posterior lobation 

 of the cephalic disk, different colour, and apparent different position 

 of the branchial plume. 



Doridium cyaneum, D. nigrum, and D. guttatum, described by Dr. 

 Von Martens from the Indian Ocean, have not yet been figured. 

 Until all these exotic species have either been compared or much 

 more amply described and illustrated, there will remain much un- 

 certainty respecting the identification of all or any one of them. 



126. Pleurobranchus angasi. (Plate VI. figs. K, K 1.) 



Animal (in spirit) uniformly pale buff, elongate ovate. Mantle 

 probably smooth in life, wrinkled by contraction, not very widely 

 produced at the free margin. Foot broad, tapering behind, roundly 

 subtruncate in front, where there is a thickening forming a double 

 margin beneath the proboscis. The frontal veil is straight in front, 

 angular at the sides, which are grooved. Tentacles shortish, slit at 

 the outer side, with the minute eye-specks at their base behind. 

 Branchial plume consisting of about sixteen leaflets. Penis spine- 

 like, very acute, and slightly curved at the tip. 



Shell placed well forward, the pale apex being posterior. It is 

 brown in front, glossy, and beautifully iridescent on the exterior. 

 It consists ot about a whorl aud a half, the nucleus being spiral and 

 hollow within. The last whorl is much prolonged by additional 

 strongly defined concentric layers, and also ornamented with fine 

 Mt distinct transverse striae. The columella is arcuate, and has an 

 umbilical groove parallel with it. 



