i 27 



scutum. It consists of about 8 divisions, separated by prominent transverse ridges, each of which 

 is curved with the curvature away from the extremity. The base of the latus corresponds vvith 

 4 (indistinctly 5) of the underlying scales. 



The c a r i n a is very long and rather narrow, curved longitudinally and strongly bowed 

 laterally, hence very distinctly concave over its whole length. lts extremity stands off and 

 reaches higher up than that of the tergum. The middle row of knobs described by Borradailk 

 very distinct. 



The rostrum composed of 4 (in the smaller specimen 3) divisions, small and narrow, 

 its base bordered by a row of five scales (fig. 13^). 



The peduncle is rather thick, swollen and not very long: as long as the capitulum 

 in the smaller specimen, about twice the length of the tergum in the larger specimen. The 

 upper scales (fig. 14) are broad and distinctly crenated; those of the second whorl are half or 

 one third the size of those of the upper whorl and are so placed that one is exactly under 

 the centre of an upper scale and another between two of these. The scales of the third and 

 fourth whorls are much smaller ancl not placed so regularly ; then follow still smaller ones, 

 rounded calcareous beads invisible to the naked eye, which are distributed over the whole 

 surface of the peduncle. 



The colour of the capitulum and the peduncle is a dark, beautiful brown, the tip of 

 the tergum and the rows of scales immediately underneath the capitulum being white. 



Size. The length of the largest specimen, including the peduncle, is 25 mm., the length 

 of the carina in the same specimen being 9 mm. 



The two specimens were collected at Labuan Pandan, which is on the east coast of the 

 island of Lombok. 



Observations. Perhaps Darwin's L. catita comes nearest to this species ■ the 

 specimen Darwin made use of for his description was only 5 mm. in length including the 

 peduncle, and may not have been fullgrown. 



The smaller specimen of the two collected by H. M. S. "Siboga" has the tips of some 

 of the valves (tergum and carina) broken off and the space between the slightly distended 

 valves is filled up with dirt; a small specimen of Ibla (? Cumingi Darwin) was found attached 

 to the inner side of one of the valves. 



4. Lithotrya truncata (Quoy et Gaimard). 



Of this curious species, which was founded for specimens from the Friendly Archipelago, 

 and was known to Darwin from specimens from the Philippine Archipelago, two specimens 

 were collected during the cruise of the "Siboga" at: 



Stat. 60. 27 — 28 April 1899. Haingsisi, Samau Island, Timor: Shore exploration. 



They are small specimens: the largest of the two measures (capitulum and peduncle 

 together) about 1 1 mm. A very small specimen of what I believe to be an Alepas (perhaps 

 identical. with the Alepas lithotryae I found attached to L. nicobarica) occupies the corner 

 between the tergum and the carina where the rudimentary latus is to be looked for. 



127 



