82 NILS HJ. ODHNER, STUDIES ON RECENT CHAMIDAE. 



group in queation. In the P. radians section, however, the shape is evidently sub- 

 ject to considerable variation. 



In the subgenus Echinochama, which contains only two recent species from the 

 coast of America (E. arcinella Linné and E. califomica Dall) the sculpture has 

 been strangely differentiated into radially arranged spines. This unique sculpture, 

 which finds its correspondence in the spinosa group of Chama, is probably of late 

 origin and may perhaps justify the raising of this subgenus to generic validity; this 

 is, of course, a matter of subjective comprehension. Dall & Simpson (1902, p. 496) 

 state that the shell is usually detached before it becomes adult. 



Geographical distribution of the Chamidae. 



The distribution of Chamidae presents three separate geographical centra, one 

 oriental and comprising the Indian ocean and adjacent parts of the Pacific, and 

 characterized by the subgenus Eopseuma and species such as Ch. lazarus, reflexa and 

 spinosa, P. cristella and retroversa. The second chief centrum exists on the coasts 

 of America; is seems to have its source in the Antillan region, from where it has 

 given offshoots to both coasts of N. and S. America. Characteristic of this region 

 are the subgenus Echinochama and species such as Chama sinuosa and Pseudochama 

 radians. No species of the family seems to be distributed över both regions, with the 

 possible exception of Ch. spinosa, which is stated by Carpenter (1864 and 1873), 

 to be known from the west coast of California and from Panama and otherwise is 

 found throughout the Pacific and the Indian Ocean as far as the Red Sea. The state- 

 ment that Ch. lazarus comes from the West Indies (Anthony, 1905, and W. R. 

 Rush, »Nautilus» 1891) is certainly due to the fact that Ch. lazarus of Lamarck 

 is different from the Linnean species and synonymous with Ch. macerophyUa (ef. 

 Lamy 1917). 



Between these chief centra there protrudes a smaller one, the Mediterranean, 

 characterized by Chama gryphoides and allies and Pseudochama gryphina; it extends 

 to the Azores on the one hand (Ch. gryphoides; Dautzenberg & Fischer 1897), 

 and to Cape Verde Islands on the other (P. gryphina; Dautzenberg 1910). 



The northern limit of the Chamidae in the Atlantic is, on the European side, 

 the coast of France, from where Dautzenberg has described a new species, Ch. 

 nicolloni. According to Jeffreys, further, Ch. gryphoides has been dredged at Cape 

 Breton (ef. Dautzenberg 1892). A statement is also made by Christensen (1907) 

 that one specimen of Ch. gryphoides has occasionally been caught on the west coast 

 of Denmark; the author thinks that it has fallen from the bottom of a ship. On 

 the American side Cape Hatteras is the northern limit of Chama as well as Pseudo- 

 chama (Dall 1889). Southward the family extends to the coast of Brazil; Dall 

 (1891) states the occurrence of Ch. congregata at Santa Caterina (26° S.). The 

 southernmost habitat of a Chama (crenulala) on the west coast of Africa is S. Thomé 

 (Tomlin & Shackleford 1914). On the east side of South Africa a species of 

 Chamidae was caught and is mentioned by Bartsch (1915) under the name of 



