21 



Akca biangolata. Arca tesid ohlongd, ventricosd, al6d, ra- 

 diatim costatd, ejndermide fiiscd setosd indutd ; margine dorsali 

 antice actite, postice ohtuse angulatil ; latere antico breviore, al- 

 tiore, postico subucuminato, margine laterali declivi ; ared liga- 

 menti elongatd, antich latiore, pland : long. 2*, lat. 1*2, alt. 1'3 

 poli. 

 Hab. ad littora Columbiae Occidentalis. ( Atacamas.) 

 A siiigle specimen was dredged at a depth of seven fathoms. — 

 G. B. S. 



Arca multicostata. Arca tesid ovato-rhombed, albd, radiaiim 

 .multicostatd, epidermide fuscd subvelutind indutd; latere antico 

 superne anguLato, subtus rotundato, postico superne angulato ; 

 maro-ine laterali declivi; carind rotimdatd ex umbone ad mar- 

 ginėm inferam posticam decurrente ; costis rotundatis, minu- 

 tissime decussatis, anticis siibgranosis ; sidcis rotundatis; ared 

 ligamenti latiusculd: long. 2-8, lat. 21, alt. 2-4 poli. 



Hab. ad oras Americse Centralis. 



Dredged frora a depth of tvvelve fathoras in the Gulf of Tehuan- 

 tepec. — G. B, S. 



§ § Inseąuivalves. 



Arca obesa. Arca testd ovatd, ventricosd, albd, radiatim costatd, 

 epidermide fuscd squamosd obtectd ; costis numerosis, confertis, 

 planulatis, Icevibus ; latere antico breviore, postico subangulato ; 

 ared cardinali breviusculd, angustd : long. 1*55, lat, l"l, alt. 1*1 

 poli. 



Hab. in Columbift Occidentali. 



A few specimens oniy were dredged, in seven fathoms, at Ataca-. 

 mas. — G. B. S. 



Akca i-abiata, Arca testd brevi, guadraio-globosd, albd, radiatim 

 costatd; costis anticis, valvce majoris prcecipue, rugulosis, posticis 

 latioribus Icevibus, omnibus planulatis ; latere ayitico breviore, 

 rotundato, postico longiore, subangulato ; ared ligamenti latd, 

 rhomboided; epidermide fuscd : long. 1-2, lat. 1-, alt. \-\poll. 



Hab. ad Real Liejos et ad Tumbez. 



Dredged among sandy mud at a depth of seven fathoms. The 

 epidermis at the posterior edges o*' the ribs is sėtose. — G. B. S. 



Arca labiosa. Arca testd brevi, ąuadrato-globosd, albicante, ra- 

 diatim costatd, costis anticis, valvce majoris prcecipue, granosis, 

 posticis IcEvibus i latere antico breviore, superne dngidato, itfrU 

 rotundato ; postico longiore subangulato ; ared ligamenti an- 

 gustd ; epidermide tenui, fuscd: long. 1*45, lat. 0"9,. alt. ri5 

 poli. 



Hab. ad Tumbez, Peruviae. 



A few specimens only were dredged, in soft raud, at a depth o f 

 seven fathoms. — G. B. Š. 



