4 NILS H.I. ODHNER, STUDIES ON RECENT CHAMIDAE. 



Many modern authors who have dealt with forms of Chamidae mention the 

 difficulties caused by the absence of a good monograph of the group. Antoky (1905) 

 gives his experience in the following words (p. 287): »je me vois dans l 1 obligation 

 de signaler, ayant malheureusement eu å en faire 1'expérience, Tinsuffisance des mono- 

 graphies de ce genre contenues dans les traités précités et 1'intérét qu'il y aurait a 

 faire actuellement une revision compléte du G. Chama, au point de vue systémati- 

 que». Lynge (1909) makes the following statement (p. 264): »It is very disheart- 

 ening to look through the literature of the species of the genus Chama and of their 

 distribution, because of the uncertainty and casuality which prevail in it; this is of 

 course for the greater part due to the bad diagnoses and figures in which the charac- 

 teristic marks of distinction, e. g. in the sculpture, are disregarded, and instead are 

 given long descriptions of insignificant and usually individual details pertaining to 

 colour and outline; but certainly authors are often too careless in determining solit- 

 ary specimens without having a large quantity of material at their disposal for coni- 

 parison — better no determination than an erroneous one. It is very eharacteristic 

 when Ed. v. Mårtens saj^s: 'Die Arten dieser Gattung sind sehr schwer gegen- 

 einander abzugrenzen, daher ihre Bestimmung und Benennung of t etwas willkiirlich', 

 and A. H. Cooke: 'It would be impossible here to éntef into a discussion of the 

 facts in the case of a genus notoriously so variable as Chama, when Reeve has 

 made fiftyfive species out of material probably better represented by ten 1 ». 



These quotations may be sufficent to illustrate the opinions of the authors who 

 have been engaged in studying forms belonging to Chamidae. There exist as a m ätter 

 of fact two antiquated monographs on the »genus Chama-», one published by Reeve 

 (1847) in his Conchologia leonia, vol. 4, the other issued by Clessin (1887) and 

 forming part 8: 5 of Martin i & Chemnitz, Conchylien-Cabinet. The last-named 

 publication is for the most part a def icient copy of Reeve ; the descriptions as well 

 as the figures are bad and, with few exceptions, almost valueless for determination. 



The most recent literature on the morphology and the anatomy of Chamidae 

 (Anthony 1905, Pelseneer 1911, Grieser 1913) is chiefly descriptive and based on 

 very small material, thus not exhibiting specific details useful for giving an idea of 

 the mutual affinities] and practicable for a systematical arrangement of the forms. 



Even the descriptions which take into consideration exclusively the shell 

 characteristics are genera] ly given by the various authors in such a manner that an}' 

 attempt to arrange the fonns systematically has hitherto been impossible. The 

 existing literature on the shells of Chamidae is so confused that a thorough investi- 

 gation, from a critical point of view, is necessary in order to solve the problems 

 and lead towards a satisfactory knowledge of the matter. 



i. The liingc stnicture of the adnlt Cliamid.ie. 



The most striking fact with regard to the shell is the mode of its attachment 

 to the substratum. Part of the forms are attached by their left val ve; this is the 



