KTJNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 59. N:0 3. 77 



how rich in synonyms Ch. reflexa is; 1 to tliose I mentioned then may be added Ch. 

 carditaejormis Reeve, which has proved, according to materials at my disposal, to be 

 only a peculiarly elongated modification of Ch. reflexa, while the more rounded shell 

 has, for example, been described by Clessin as Ch. billowiana. 



Not only the shape but also the sculpture may be influenced by the surround- 

 ings and vary in accordance to the local conditions. This is exemplified by Ch. spinosa 

 Bröd. In its typical state its sculpture consists of densely set produced spines on 

 the upper val ve and more sparse spines as well as lamellae on the lower one. The 

 latter has also a strongly produced, spirally twisted, apex and is rather thin. These 

 characteristics are preserved when the shell is attached to an unchanging substratum. 

 When fixed on corals, however (as, for example, some specimens collected at Tama- 

 ta ve, Madagascar, by Dr. Kaudern) 2 these characteristics are obvious only in young 

 specimens. In older ones the left valve is intimatety and with its whole surface 

 accrete to the substratum; this is evidently due to the increase of the coral, and 

 the upper valve is more or less covered by a lime crust, also deposited by externa! 

 agents (algae). In this case both valves have a thicker structure and shorter spines 

 than those which are attached more freely. That both forms are identical is proved 

 by the similarty shaped under valve as well as by the sculpture of young individuals. 

 The thicker shells are probably identical with the form which Clessin has described 

 under the names of Ch. parvula and granulata, while the thinner and more spinose 

 type seems to be identical with Clessin's Ch. fragum (which is not synonymous 

 with this form of Reeve). 



The last-named example illustrates what an important influence the growth 

 has on the shape and sculpture. In this connection I give as my opinion that, in 

 all probability, the form which Clessin (1889) has named Ch. lamarckiana and which 

 may be identical with Ch. bermudensis Heilprin 1890, is nothing but a form of in- 

 crease of Ch. sinuosa. In the collections of the State Museum (Riksmuseum) there 

 exists a specimen from the coral reef of Bermuda collected in 1889 by Dr. Fors- 

 strand. A careful comparison of this specimen with other Chamas from the West 

 Indies has given the result that it shows a close agreement with large specimens of 

 Ch. sinuosa, except for the fact that it is extremely solid. Because of its solidity 

 as well as of the incrustation of algae and other lime-depositing organisms, no exact 

 idea of the original sculpture is obtainable, but a tendency to the formation of lobes 

 in the margins is traceable and there exists a faint trace of the posterior radiating 

 furrow that is characteristic of the species in question. lnteriorly Ch. lamarckiana 

 agrees with this species in having a similar course of the mantle line relative to the 

 adductor scars, as well as a similar colour (greenish white), lustre and smoothness. 



1 From these, I think, must be excluded Ch. rilppetti of M'Akdrew (different from that of Reeve, which 

 is a Pseudochama, probably synonymous with P. cornucopia). The species in question, which seems to corre- 

 spond entirely with Ch. porösa of Clessin, differs in some respects from Ch. reflexa, and is probably identical 

 with Ch. iostoma of Anthony, which originates from the Red Sea. According to Lamy 1917 this latter is 

 synonymous with Lamarck's Ch. Minbula. 



2 Of. Odhner 1919, p. 30, pl. 3, tigs. 35—39. 



