KTJNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 59- N:0 3. 83 



»Chama gryphinal» (»a rather poor specimen»). At Madagascar and Réunion some 

 species of Chama occur (Riksmuseum; Deshayes 1863), and in Western Australia 

 the southernmost limit is Geraldton (Ch. spinosa; Verco, Hedley 1916), on the east 

 coast the southernmost locality is Port Jackson, from where E. A. Smith (1885) reports 

 the same species. From New Zealand no member of the family is knovvn. On the 

 west side of America Chamas range from San Francisco (Ch. pellucida; Carpenter 

 1864) to Valparaiso and Juan Fernandez Islands (Dall 1909, the same species); 

 Pseudochama has a more restricted distribution on this coast. In the Pacific the 

 most extreme localities of Chamidae are Japan and the Sandwich Islands on the 

 one hand and Lord Hood's Island on the other. 



This survey shows that the recent Chamidae are restricted to the regions of 

 constant warm streams (with few exceptions) ; f urther that they inhabit coral reefs 

 especially. Clessin describes (1889) a Chama maculata from Magellan Strait, but 

 this is certainly inaccurate. 



No species of Chamidae is known to inhabit both the west and east coast of 

 the Isthmus of Panama. That an early communication has existed across this bridge 

 of land is, however, shown by the fact that the West Indian Echinochama arcinella 

 is replaced on the western coast of America by a closely allied form, E. calijornica 

 Dall. On the other hand, an immigration seems to have taken place from the 

 Caribbean subregion eastward ; Chama crenulata from the west coast of Africa seems 

 to be closely related to Ch. macerophylla, a faunistical relation supported by the 

 occurrence of many identical species on the opposite coasts of the tropical Atlantic. 



Fossil forms of Chama and Pseudochama. 



As early as in 1814 a fossil Chama was described by Brocchi, who in this 

 year established his Ch. (Pseudochama) sinistrorsa, a name which had previously been 

 taken by Bruguiére (1792) for an other species; ef. Cossmann & Peyrot 1911); 

 the name must therefore yield to the synonymous Ch. gryphina of Lamarck (1819), 

 contrary to the statement made by Weinkauff (1867). Lamarck in 1819 also de- 

 scribed one fossil species of Pseudochama (laevigata) as well as six Chamas. He 

 gives, however, no statements as to their geological occurrence. 



The oldest fossil Chamidae are reported from the cretaceous s}stem. Stoliczka, 

 who gives (1871) a list of all forms known by him from cretaceous strata, makes 

 the following remarks about them (p. 231): »We have no distinct account of any 

 species of true Chama occurring in the jurassic period, and even in the cretaceous 

 there are only few species known with sufficient certainty, others more resemble in 

 form Diceras and Pequienia.» This is especially the case with some that are attached 

 by the right val ve, for example Ch. cornucopiae of d'Orbigny (1847) and Ch. haueri 

 of Zittel (1865). The former is very different from a Pseudochama on account of 

 its longitudinally ribbed shell. About Ch. haueri Zittel states in his diagnosis (p. 

 147): »Välva major tumida, profunda, affixa vel libera, sinistrorsa»; a similar in- 

 differently fixed or free state is known only in Echinochama. As, in addition, the 



