206 



PROF. E. VON MARTENS ON THE SHELLS 



as marine by the label " Lampee, 7 fathoms, 14. 1. 82." Never- 

 theless the whole appearance of the shell is that of the genus 

 Dreissena, which lives in fresh and brackish water. The marine 

 subgenus Septifer, which agrees with Dreissena in the presence of 

 a septum on the iuside of the umbones, is further distinguished by 

 radial furrows at the outside, which are wanting in our species. 

 But the essential difference between both genera is in the soft 

 parts, the edges of the mantle being united for some extent on 

 the basal part in Dreissena, whereas in Septifer they are quite free 

 in that region. In one of Dr. Anderson's specimens portions of 

 the mantle in the dry state are present and show no trace of 

 coalescence at the lower side. For this reason, and also from its 

 habitat, this species is to be referred to Septifer until further 

 evidence is forthcoming. 



D. carinata, Dunker, Dissert, de Septiferis et Dreissenis, 1885, 

 p. 15, seems, according to the description, rather near to this 

 species ; but on comparing the type in Dunker' s collection it is 

 found to be a much smaller shell, of much narrower shape, and 

 different coloration. 



304. Modiola olaberrima, Dunker, P. Z. S. 1856, p. 363 ; 

 Reeve, Conch. Icon. x. pi. viii. fig. 48. 



Elphinstone Island. Canton, Australia. 



305. Modiolaria arcuatula, Hanley, Reeve, I.e. x. Modiola, 

 pi. vi. figs. 27 & 28. 



Elphinstone Island. Singapore. 



306. Modiolaria nana, Dunher, Reeve, I. c. x. Modiola, pi. x. 

 fig. 01). 



Sullivan Island, 6 fathoms. Port Lincoln (Australia). 



307. Lithodomus gracilis, Philippi, Abbild. Modiola, pi. 2. 

 fig. 1 ; Reeve, I. c. x. pi , i. fig. 4. 



Elphinstone Island. Malacca, China Sea. 



308. Lithodomus teres, Philippi, loc. cit. pi. 1. fig. 3. 

 Blphinfltone Island; Sullivan Island; Owen Island, in coral. 



Mauritius, Seychelles, Pacific. 



809. LiTHO domun nasuta, Philippi, loc. cit. pi. 1. fig. 2; 

 Reeve, I. e. x. pi. ii. fig. 10. 



Owen Island, coral-burrows. Zanzibar, Japan; also in the 



A thru lie. 



310. LmronoMUS malaccana, ffanley, Reeve, Z.c.x.pl.iv. fig.20. 

 Sullivan Inland and Owen Island, in coral. Malacca. 



