AN ATIN A. 



Plate I. 



Genus ANATINA, Lamarck. 



Testa aquivalvis, inirquilateralis, tenuis, hyalina, argenteo- 

 alba, Imvlgata, interdmm circa nmhones concentrice pli- 

 cata, versus margims plus minus yranulata, granidis ad 

 latus posticum in lineam de umbonibus abrupte cessan- 

 tibus, latere aiitico rotmuhto, postico in rostrum ex- 

 pansum plerumque producto, Interibns amholjus liianti- 

 Ims. Cardo processu cochlearifornii, sepfo obliguo sus- 

 tentato, in ntrdque valvd, ligamentum continente, com- 

 positus. 



Shell equivalve, inequilateral, thin, hyaline, silvery white, 

 smooth, sometimes concentrically plicated around 

 the umboes, more or less granulated towards the 

 margins, granules abruptly ceasing at the posterior 

 side in a line from the umboes, anterior side rounded, 

 posterior generally produced into a pouted beak ; 

 both sides gaping. Hinge composed of a spoon- 

 shaped process, supported by an oblique septum, in 

 each valve, containing the ligament. 



An interesting genus of the Mya tribe, ranging along 

 the eastern shores of the eastern hemisphere from Japan 

 to Tasmania, and even to the Antarctic Ocean, with veiy 

 little variation in the general typical character of the shell. 

 There are, however, two well-marked forms of Jnatina, 

 one in which the posterior side of the shell is broadly 

 truncated, as in A. truncata ami elliptica, the other, much 

 the more numerous in species, in which the posterior side 

 is produced into a pouted beak, gaping, of course, in both 

 forms for the passage of the siphons, which arc united 

 throughout their length in one sheath. The shell of Ana- 

 tina is invariably thin and hyaline, and of a silvery white- 

 ness, crowded towards the margins with fine grains, which 

 abruptly cease on the posterior side where the shell com- 

 mences to be beaked, that is to say, on a constricted line 

 sloping from the umboes. 



The hinge of Anatina is composed of a jirominent 

 spoon-shaped process in each valve, developed rather ob- 

 liquely in a direction posterior to centre, and supported 

 by a firm septum. There is also a tine linear septum in 

 front of it, and both radiate towards the interior. The 

 hinge processes work n|)on each other with the aid and 

 action of a contained elastic ligament. 



Of the thirty species described in the following mono- 

 graph the habitats of twenty-two are known. Two are 

 from Japan, six from the Philippines and Moluccas, one 

 from Borneo, one from Ceylon, eleven from Australia and 



Tasmania, and one, a \'ery remarkable species, from the 

 island of New South Shetland, in the Antarctic Ocean. 



Species 1. (Mus. Cuming.) 



Anatina Cumimgii. Jnat. testa ovaid, tiimidiusculd, 

 teniii, hgalind, versus marginem posticum profuse 

 granulald, latere antico compresse rotundato, postico 

 constricto-rostrato, concentrice corrugato, expanso- 

 hiante. 



Cuming's Anatina. Shell ovate, rather swollen, thin, 

 hyaline, profusely granulated towards the posterior 

 margin, anterior side corapressly rounded, posterior 

 constrictedly beaked, concentrically wrinkled, not 

 granulated, expandedly gaping. 



Valenciennes, MS. in Mus. Cuming. 



Hab. ? 



This elegant species is chiefly distinguished by its con- 

 strictedly pouted posterior extremity being concentrically 

 w'rinkled. 



Species 2. (Mus. Cuming.) 



Anatina siphonata. Anat. testa subabbreviuto-ovntd . 

 medio tumidd, tenui, hyalina, circa umbones concen- 

 trice plicatd, versus marginem posticum profuse gra- 

 nulatd, latere antico rotundato, postico attenuato et 

 constricto-rostrato, remote concentrice corrugato, liaud 

 grannlato, subtubuloso-ltiante. 



The spouted Anatina. Shell rather shortly ovate, 

 swollen in the middle, thin, hyaline, concentrically 

 plicated around the umboes, profusely gramdated to- 

 wards the posterior margin, anterior side rounded, 

 posterior attenuated, and constrictedly beaked, dis- 

 tantly concentrically wrinkled, not granulated, some- 

 what tidiularly gaping. 



Hab. Borneo. 



Allied to the preceding species, but a shorter form, with 

 the posterior extremity even more attenuated and con- 

 strictedly pouted. 



Species 3. (Mus. Cuming.) 

 Anatina eullata. Anat. testa snbquadrato-ovald, gib- 

 bosd, subhyalind, concentrice suhrugoso-striatd, latere 

 antico late tumido-truncato, postico attenuato,Jlexuoso- 

 rostrato. 



February, 1SG3. 



