﻿G A S T R C H .E N A. 



Pl.ATK I. 



GemiR GASTROCH^XA. Lamarcl: 



.Mcll.l.LSCUM ACEPlIALOrODl'M, PERFOIiASS, TUBICOLI'M. 



T''gta hlrahi.1, i)i(equilaieral>s, (fijuivalvis, antice 

 ml marijinem vcntralem late liians, itmbonihiis 

 iiiiticvferi temnnalibvs ; cnrdo dindibns lilerumquc 

 ^I'hinconspicuis ; ligameuivin r.rtfrnwii ; tuba 

 null liuiiquam ferd lilera. 

 Moi.i.i'SK ACEl'HALOPODE, perforating, tubc-inhabit- 

 iii!^. Shull bivalve, inequilateral, cqnivalve, 

 widely gaping iu front at the ventral margin, 

 umbones almost terminal in front ; hinge for 

 tiie most part with inconspicuons teeth ; liga- 

 ment external ; tube sometimes nearly free. 



The G-astrochiBna; for the most part live, like the 

 Pholades, in hollows which they bore in limestone 

 rocks, and which they line with a shelly tube ending 

 ill a narrow neck, like a bottle. But some of them, like 

 the Gai'troelia:na dichia, make an almost independent 

 tube, only attached by the neck or by one side to the 

 shi>ll or rock through which they have bored, or to 

 which they are otherwise fixed. There is a speci- 

 men in the British Museum of O. ihihia in which 

 the substance bored through and slenderly lined is 

 crystallized carbonate of lime. The British species 

 is common to France and many other European 

 coasts. The Indias, East and West, the Gallapagos 

 Islands, the Mauritius, South America, the 

 Pacific Islands, produce many species, and a small 

 number were described by the late M. Deshayes, 

 when in London some years since, which had been 

 collected by the late Mr. Cnming in the Philippines. 



Species 1. (Fig. a, b, c. Mus. Brit.) 



Gasteoch.ena ovpax. Gas. testa tcniii, elonijotd, ob- 

 liqud, tenuiter striata ; hiatu ventrali mediocri, 

 prope medium terminauti ; cardine tcniii, fire 

 edentulo. 



The doubtful Gastroch.exa. Shell thin, elongated, 

 oblique, finely striated ; ventral hiatus moderate, 



terminating near the middle; hinge thin, al- 

 most without teeth. 



Pennant. British Zoology. 



GastrocJuvna modiolina. Lamarck. 



Rocellaria dubia. Adams. 



Hah. British MediteiTanoan coasts. 



The bottle-shaped tube which covers the valves 

 and syphons of this .species is composed, when free, 

 of agglutinated sand and small pebbles ; when en- 

 closed, it forms a calcareous lining to the crypt. 



Species 2. (Mns. Brit.) 



Gast 



./</,(■, 



ra/.;, r,,„l„l,„l„t<l, .odfalo-nnjat,;, ,ul l,n„;,i,n„ 

 truncatd, area dorsali depressd, rrdii'^i-id,!, niktt 

 mediond postice in sulciim olliqinini trnniiniuti : 

 hiatu dongalo. 



The plaited Gasteoch^na. Shell sub-compressed, 

 covered with a brown epidermis, tortuous, with 

 the posterior area elevated, confabulated, wrin- 

 kled with sulci, truncated at the end, dorsal 

 area depressed, rather straight, middle area pos- 

 teriorly terminating in an oblique groove ; 

 hiatus elongated. 



Deshayes. Proc. Zool. Soc. 18-54, p. 329. 



Hab. Isl. Zebu, PhiHppLnes. 



The shell very much resembles G. rostnita, but the 



plaits on the posterior area are finer, and less deeply 



cut, and the dorsal area much less projecting. 



Species o. (Mus. Brit.) 

 GASTRnCn.ENA EREVIS. Gcis. tfstd iiiflatd, brevi, so- 



lidiiisridd, Iceriilscidd, antirc gibbosu. hiatif rahtr 



arcuato, brrvi. 

 The SHORi' Gastroch.ena. Shell inflated, short, 



rather solid, rather smooth, gibbous anteriorly ; 



hiatus strongly arched, short. 

 SowERBY. Proc. Zool. Soc. 18.34. 21. 

 Hab. r 



