bloomer: anatomy op cultellus a.s'd azob. 9 



anterior part is foldt-d upon itself in a somewliat similar manner as in 

 Solecurtus strigillatus. 



The anterior adductor muscle (Fig. 3, A. A.) is similar, but smaller. 

 The posterior adductor (Fig. 3, A^.) is deeper, angular on the antero- 

 dorsal surface, and is situated more ventrally. The siphonal tubes 

 (Fig. 3, Ex.S.' , In.S.') are more compact, though very muscular. 



In transverse section the arrangement of the muscles of the inhalent 

 siphonal tube appears to be very similar to that of Solecurtus 

 Htrigillatus and Tagelus gibhm ; it is also akin to that of Psammobia 

 vespertina, as described and illustrated by Rawitz in Ber Mantelrancl 

 der Acephalen, and by myself On the Anatomy of the British Species 

 of Psammohia, wliilst in the distribution of the nerves there is still 

 a closer resemblance. A tentacular fringe is present all round the 

 ventral portion of the mantle from the anterior adductor to the 

 posterior adductor muscle, but it is more pronounced at the anterior 

 and posterior ends. "What, however, is the chief characteristic, in 

 fact a striking feature of the animal, is the mass of tentacular 

 processes, which covers the entire external surface of the siphonal 

 tubes. This is in great contrast to the British and Mediterranean 

 species of A. atitiquatns, which are quite bare. The bifurcations of 

 the retractor pedis posterior muscle (Fig. 3, P.P. P.) are longer, and 

 their terminal parts are situated on the dorsal, instead of the dorso- 

 anterior, surface of the posteiior adductor muscle. 



The alimentary canal also varies. The oesophagus is a little 

 shorter, the stomach more compact, being shorter and deeper, and 

 the intestine makes a larger number of folds before turning 

 posteriorly. 



From the foregoing description of the British specimen of 

 A. (intiquatus, the type of the subgenus Azor, it will be observed 

 that it differs considerably from the genus Psmmnosolen, Risso, 

 type S. strigillatus (Linne),' and more so from the genus Solecurtus, 

 Blainville, type Solen legumen (Linne),' consequently Azor should 

 be raised to tlie position of a genus; further, tlie Japanese is quite 

 distinct from the English species and bears out the justification of 

 treating it as a separate species, but whether it agrees in its structure 

 with the animal of the ^'icobar shell described by Chemnitz, the tyi)e 

 of coarctatus, I have as yet been unable to determine, as I have not 

 succeeded in obtaining a specimen from that locality. At the same 

 time I shall not be surprised to learn later that the Japanese 

 specimen, owing to the peculiarity of the mantle fringe and the 

 siphonal tentacular processes, is only local, and consequently will 

 have to be made a distinct species. 



In the work of Dr. Dall just referred to he states " The Solenidse 

 form a compact group after the elimination of the soleniform 

 Psammobiidae such as Novaculina and Tagelus^', but to this exclusion 

 must be added the genera Azor and Psammosolen (in the latter as far 

 as S. strigillatus, S. candidus, and S. Philippinaruni are concerned). 



' Dr. W. H. Dall, "Tertiary Fauna of Florida": Trans. Wagner Inst. 

 Phil., vol. iii, pt. ii, p. 9-51, 1900. 



