A R ( A. 



Species ">G. (Mus. Hanley.) 



Arca Indica. Area testd subquadrato-ovatd, tenuiculd, 

 inaquivalvi, latere untie* bn i issi w, poi 



albidd, viridescente linctd, epidermide tenui, 



iter costas selosd, indutd; radiatim costatd, 



costis duabus vel tribus et triginta, omnibus versus 



maryinem sulco divisis, lull ribns umbones versus Sub- 



tilissimt crenulatis ; umbonibus approximate; liga- 

 menti ared nulld. 



The Indian Auk. Shell somewhat squarely oval, 

 rather thin, inequivalve, anterior side very -hurt , 

 r a little compressed ; whitish, stained with 

 green, covered with a thin brown epidermis, bristly 

 between the ribs; radiately ribbed, ribs two oi 

 three and thirty in number, all divided by a groove 

 towards the margin, very finely crenulal 

 side towards the umbones ; umbones approximated ; 

 no ligamentary area. 



Gmeli.v, Lamarck, Anim. sans vert. (Deshayes' edit.), 

 vol. vi. p. 473. 



Hab. ? 



This and the Arca brerifrons are the only spi 

 ribbed Area in which there is no ligamentary area, and 

 in the Area Indira this condition of the hinge occasions 

 a very peculiar modification of the teeth. The teeth 

 posterior to the umbones are very small, and are set in 

 a fine row as in the hinge of Nucula ; but those anterior 

 to the umbones are larger, very few in number, and 

 jumbled together, as it were, in a small rude cluster. 

 Another peculiar feature in this shell is, that the whole 

 of the ribs of both valves are divided by a groove towards 

 the margin. 



Species 57. (Mus. Cuming.) 

 Abca angicostata. Area testd subquadrato-ovatd, sub- 

 aquivalvi, lateribus superne angulatis, infra rotun- 

 datis, antico brevi ; albidd, fuscescente partim tincld, 



epidermide fused, inter costas squamosa, indutd; 

 radiatim costatd, costis ad triccnas, anticis angustis, 

 snbdistantibus, leviter crenulatis, jmstieis latiorihus, 

 expansioribus ; ligamenti ared latiusculd. 

 The narrow-ribbed Ark. Shell somewhat squarely 

 oval, nearly equivalve, sides angulated at the upper 

 part, rounded beneath, anterior side short ; whitish, 

 partially stained with light brown, covered with a 

 brownish epidermis that is scaly between the ribs ; 

 radiately ribbed, ribs about thirty in number, the 



anterior narrow, rather distant, and slightly crenu 

 latcd, the posterior wider and more expanded ; area 

 of the ligament rather wide. 

 Reeve, I'm. Zool. Soc, 1844. 



Hab. ■ ? 



There is a very unusual disproportion in the width of 

 es, the anterior ribs being exceed- 

 ingly narrow, whilst the posterior are wider and spread 

 out as it were. 



Species -~> s . (Mus. Cuming.) 

 Abi \ LORICATA. Area testa siibqiiudrutu, gihbosu, late- 

 ribus superni attenuato-angulatis, antico brevi, ro- 

 tundato, postico angulato-extenso ; albidd, corio cor- 

 nea ceeruleo-viridescente loricatd, epidermide tenui, 



fused, inter costas squamosa, indutd ; radiatim cantata, 



costis septem vel octo et viginti, planiusculis, acutan- 

 (julis ; umbonibus subapproximatis ; ligamenti ared 



leci/i r declivi. 

 The HAILED Auk. Shell somewhat square, gibbous. 



-ides attenuately angled at the upper part, ant( rioi 



side short, rounded, posterior angularly extended; 

 whitish, covered with a strong homy bluish green 

 cuticle, and a thin brown epidermis that is seal) 

 between the ribs; radiately ribbed, ribs seven or 

 eight and twenty in number, rather flat, sharp- 

 angled; umbones somewdiat approximated; liga- 

 mentary area slightly bent inwards. 



Reeve, Pro. Zool. Soc., 1844. 



Hab. ? 



This shell is covered with a peculiarly strong horny 



cuticle, and differs from any previously described species 



in the arrangement and formation of the ribs. 



Species 59. (Mus. Cuming.) 

 Arca DISPABILIS. Area testd ovatd, tenui, subcampres- 

 sd, valde incequivalvi, lateribus angulaio-rotundatis, 



latere postico subcompresso-expanso ; albidd, corio 

 cameo tenui in ruleo-viridescente, epidermide Jitscd 

 indutd ; radiatim costatd, costis sex vel septem et 

 triginta, p/ouiuscu/is, umbones versus obsolete crenu- 

 latis ; umbonibus subapproximatis ; ligamenti ared 

 angustd, declivi. 

 The unequal Ark. Shell ovate, thin, somewhat com- 

 pressed, very inequivalve, sides angularly rounded, 



March 1S44. 



