Mr. E. A. Smith on Argonauta Bottgeri. 409 



LVI. — Notes on Argonauta Bottgeri. 

 By Edgar A. Smith. 



[Plate XVII. figs. 1-6.] 



The shell of this species was described and figured by 

 Maltzan in the 'Journal de Conchyliologie/ 1881, p. 163, 

 pi. vi. fig. 7. He does not state whence his specimens came. 

 In the British Museum there are two examples forming part 

 of the Cumingian collection marked "Australia" and three 

 from " Masbate, Philippines." Two specimens from the Mau- 

 ritius were obtained from Mr. Robillard, one from the China 

 Seas has lately been acquired, and two others have recently 

 been presented by J. F. Keene, Esq., who captured them 

 near the Chagos Islands in the midst of the Indian Ocean. 



The distinguishing features of this species are the nume- 

 rous ribs and tubercles, the total absence of auricular expan- 

 sions at the sides, its constantly small size, and the fine 

 granulation (a feature not remarked upon by Maltzan), which 

 more or less covers the whole surface, producing a dull non- 

 glossy appearance. These granules are particularly dense on 

 each side near the axis. 



The tubercles upon the keels, which, as in all species of 

 Argonauta with the exception of A. argo^ alternate in the 

 two series, vary to some extent both in prominence and 

 number. In figure 1 (a copy of Maltzan's figure) the tuber- 

 cles are numerous and moderately prominent ; in figure 3 they 

 are as numerous but less feebly developed, and figure 2 repre- 

 sents the opposite extreme, in which the tubercles are fewer, 

 distant, and striking. 



The following table, including the series of specimens 

 in the Museum and that represented by von Maltzan, will 

 indicate the variation in the number of the tubercles : — 



Greatest diam- Number 



eter in of 



millim. tubercles. 



From Masbate, Philippines 40 33 



Maltzan's specimen 36 28 



From Australia 33 24 



From Masbate 33 22 



From Australia 33 21 



From China Seas 30 18 



From Mauritius 28 17 



Near Chagos Islands 28 14 



From Mauritius 27 16 



From Masbate 24 16 



Ann. & Mag. N. Hist. Ser. 5. Vol. xx. 29 



