PART VI 



SYSTEMATIC DISCUSSION 



MOLLUSCA 



The mollusca herein reported represent only a very small per- 

 centage of the valuable moUusk collections secured respectively 

 by the "Ara" World Cruise of 1928-1929, the "Alva" World Cruise 

 of 1931-1932, the "Alva" Mediterranean Cruise of 1933 and the 

 "Alva" South American Cruise of 1935. 



The Amphineura are represented by three species, namely: 

 Chiton marquesanus Pilsbry, hitherto known only from the type, 

 a unique from the Marquesas, deposited in the Philadelphia Acad- 

 emy of Natural Sciences, is represented in the "Alva" collection 

 by two fine specimens from Anaho Bay. 



Two specimens of Tonicia confossus (Gould) from the Fiji 

 Archipelago appear to be the second record of this species from 

 Gould's type locality, as well as the second deposit of this interest- 

 ing Chiton in an American museum. It is more abundantly repre- 

 sented in the Linnean Society's collection in London and in the 

 "Siboga" material at Leyden. 



The Australian species, Liolophicra gaimardi de Blainville, 

 which is very rare in American collections, was obtained at Falcon 

 Island, Palm Islands, Queensland. 



The Nudibranchiata are represented by only one species, a 

 magnificent specimen, Platydoris cruenta (Quoy and Gaimard), 

 which is apparently the only representative of this exquisite habi- 

 tant of the tropic Pacific deposited in an American museum. This 

 species, so many times reported from the New Guinea-Dutch East 

 Indies area, now has its distribution extended to Samoa by the 

 "Alva" record. 



Only seven pulmonate Gastropoda are discussed in this report, 

 two of these species being represented by larval forms. The "Alva" 

 record of a young specimen of the exquisite Haliotis naevosa 

 Martyn appears to be the first record of it from Bali. An interest- 

 ing clutch of egg-capsules of the gigantic ovoviviparous Cymbium 

 flammeum Bolten, from Southport, Australia, seems to be the first 

 example of this remarkable gastropod in an American museum. 

 The nidamental capsule of Megalatractus ariuinus (Linne) from 



