ARCA.— Plate XV. 



Species 101. (Mus. Cuming.) 

 Arca lima. Arca testd elongato-ovatd, lateribus superni 

 angulatis, antico infra rotundato, postico angulato- 

 rolundato, subejetenso ; fuscescente, fusco tinctd, pos- 

 tice fusco maculatd, epidermide tenui subtilissimi 

 setosd indutd, radiatim liratd, liris angustis, nume- 

 rosis, confertis, granosis, perpaucis mediants dupli- 

 catis; lateraliter costatd, costis rudibus, subdistan- 

 tibus, crenato-nodosis ; ligamenti ared angustd. 

 The file Ark, Shell elongately ovate, sides angu- 

 lated at the upper part, anterior rounded beneath, 

 posterior angularly rounded, somewhat extended ; 

 light brown, stained with brown, spotted with 

 brown, posteriorly covered with a thin, very fine 

 bristly epidermis ; radiately ridged, ridges narrow, 

 numerous, close-set, granulated, a few ribs towards 

 the middle duplicate, ribbed laterally, ribs rude, 

 rather distant, crenately knobbed; area of the 

 ligament narrow. 

 Reeve, Pro. Zool. Soc, 1S44. 



Hub. Islands of Burias and Corrigidor, Philippines 

 (found under stones at low water) ; Cuming. 

 The sculpture of this shell is very similar to that of 

 the Arca bvllata ; it is, however, of much finer character, 

 although the shell is more elongated and altogether 

 larger. 



Species 102. (Mus. Cuming.) 

 Arca ocellata. Arca testa elonguto -quadrata, lateri- 

 bus superni angulatis, latere antico brevissimo, infra 

 rotundato, postico elongato, infra acuminato, margine 

 venirali bysso latissimi hiante ; albidd, epidermide 

 tenui, subsetosd, indutd ; radiatim striata, striis sub- 

 tilissime crenulatis; umbonibus remotis; ligamenti ared 

 latissimd, rhombo ligamentario peculiariter ocellato. 

 The eyed Ark. Shell elongately square, sides angu- 

 lated at the upper part, anterior side very short, 

 rounded beneath, posterior elongated, acuminated 

 beneath, ventral margin very widely gaping for the 



passage of the byssus ; whitish, covered with a thin, 

 rather bristly epidermis ; radiately striated, stria? 

 very finely crenulated ; umbones remote ; area of 

 the ligament very wide, diamond-shaped, ligamen- 

 tary space ocellated. 



Reeve, Pro. Zool. Soc, 1843. 



Hab. Singapore (found in sandy mud at the depth of 

 seven fathoms) ; Cuming. 



This interesting little species exhibits a character 

 which unfortunately is not very correctly represented in 

 the accompanying figure. The dark ligamentary space 

 between the umbones is marked with a pair of oblique 

 white oval spots, one on each valve. 



Species 103. (Mus. Cuming.) 



Arca trapezina. Arca testd oblique ovatd, subtrapezi- 

 formi, depressiusculd, lateribus superni angulatis, 

 antico infra rotundato, postico angulato-rotundato ; 

 albidd, fuscescente tinctd, epidermide fused, postice 

 setosd, indutd ; radiatim liratd, liris granosis ; um- 

 bonibus antici udjectis ■, ligamenti area angustd. 



The trapeziform Ark. Shell obliquely ovate, some- 

 what trapeziform, rather depressed, sides angulated 

 at the upper part, anterior side rounded beneath, 

 posterior angularly rounded ; whitish, stained with 

 light brown, covered with a brown, posteriorly 

 bristled epidermis ; radiately ridged, ridges grained; 

 umbones situated anteriorly ; area of the ligament 

 narrow. 



Lamarck, Anim. sans vert. (Deshayes' edit.), vol. ix. 

 p. 467. 



Hab. Batangus, island of Luzon (found under stones at 

 low water) ; Cuming. 



This is not a variety of the Arca Helblingii, as M. 

 Deshayes has been inclined to suppose ; the umbones 

 are situated more anteriorly, and there is a difference in 

 the style and pattern of the sculpture. 



