30 NILS HJ. ODHNER, MOLLUSCA. 
disturbed by boring organisms and overgrown with lime crusts, for which reason 
the shells get a porous structure, a feature that has led CLessin to establish (very 
unhappily, as this is a far from essential characteristic) for this form a new species 
Ch. porosa. As to the synonyms of the species, it must be remarked that CooxEr 
(1886) is incorrect in identifying the sinistral Ch. cornucopia Reeve with the present 
species; however striking their outer resemblance may be, they belong to different 
genera, the last-named species belonging to Pseudochama. 
The characterization of this species given by Rrrve (Conch. Icon. 4, 1847) is 
not adequate, as it considers merely unessential characteristics, such as a reflection 
of the margin of the lower valve. It is very difficult to indicate the real peculiari- 
ties of the species as concerns the shell. The shell sculpture and colour vary con- 
siderably, sometimes the concentric lamellation is obvious, sometimes it is quite 
obscure and dominated by the development of the more or less depressed scales or 
spines. To the same species also certainly belong many other of REEVE’s »species», 
such as Ch. aspersa, planata, obliquata, rubea, and sulphurea.' Ch. reflexa differs from 
the West Indian Ch. echinata (in which probably are to be included Ch. sordida 
Broperie and sarda Reeve, perhaps also Ch. venosa Reeve, in that it lacks the 
divaricate sculpture of the last-named form expressed in the direction towards the 
posterior of the radiating lines and stripes along the hinder shell margin. 
xood distinctions between the different species of the Chamidae are also to be 
observed from the anatomy, as will be found from the accounts below. 
Pseudochama cristella (Lamarck) [—Chama reeveana Curssin]. 42 miles W. 
S. W., 70—72 feet (°°/s), about 6 sps, max. 1. 31 mm. — LyYNGE (1908) gives a satis- 
factory criticism of CLESSIN’s opinion as to the Chama cristella of Rrrver, which, 
according to the last-named author, is specifically distinct from the type of LaMaARcK, 
a view that cannot be maintained. The species is distributed from the Gulf of Siam 
to Java, the Moluccas, and Australia (LyNar 1909). It is at once recognized by its 
orange colour and raised crista-shaped form, due to its attachment with the front 
half of the right valve, while its hind part is sharply bent from the substratum. I 
have referred this species to a new genus, Pseudochama, which comprises the so-called 
»inverse» Chamas, opposite to the normal or dextrally twisted ones, to which the 
old name is to be restricted. A complete discussion of this opinion and_ the 
reasons for establishing the new genus will be published in a special paper; here I 
only give a summary of the distinguishing points and the characteristics of the new 
genus. The dentition of these »inverse» or »sinistral» Chamas is developed in a quite 
different manner from that of Chama sensu stricto; the final result becomes a 
feature that is somewhat like the mirror image of the dentition of a Chama, so 
that the attached valves, in the former case the right, in the latter the left one, 
grow symmetric to each other, which has given rise to a misinterpretation of the 
conditions prevailing, known as the theory of the symmetric valves, and to a new 
1. A. Smirm (1885) considers Ch. fibula and Ch. pellis phocae both of Rerye, to be identical with 
Ch. jukesi. 
