﻿S AXIC AVA. 



Genus SAXICAVA, Flcuviau dc Bellcime. 

 Testa ohlonga, tequicalvis, nigosa, ad marginem ventmlem 

 Mans. Cardo (Mate jumore minute bidentatiis, 

 (elate majore edentulus. Impressiones musadares 

 distantes ; impressione pallli postice late siuuala. 

 Shell equivalve, rugose, gaping at the ventral margin. 

 Hinge in a young state bidentate, when full- 

 grown without teeth. Muscular impressions 

 distant ; impression of the mantle broadly 

 sinuated posteriorly. 

 Stn. Bi/ssomya, Cuvier. Hiatella, Daudiii. 



The Saxicaviv are rock-burrowing moUusca. They 

 are found fixed in small hollows, often in the deserted 

 holes of the Pholas. To the inner wall of the hole 

 they attach themselves by a byssus, and often in the 

 after growth of their valves become conformed to its 

 shape. The young shells differ in two respects from 

 the older form. They have small cardinal teeth which 

 disappear when the animal is adult, and they have 

 spines on the posterior angles, which also disappear. 

 In this younger state they represent the genus Hiittella 

 of Daudin. The arctic seas, the Mediterranean, and 

 the Cape produce most of the few species known. 



Species 1. (Mus. Brit.) 



S.\xiCAVA ARCTICA. Sax. tcstd obloTigd, nigosd, crassd, 

 estate junion postice spinifcrd, cardine bidentato, 

 (Stale seniori cardine edentulo ; latere antico an- 

 gusto, brevi, margine ventrali sinuoso, vmbonihus 

 depressis, anticis ; latere postico latiori, qnadrato, 

 hiangulato, late truncate. 



The arctic Saxicava. Shell oblong, rugose, thick ; 

 posteriorly spiniferous when young, with two teeth 

 on the hinge ; without teeth on the hinge when 

 adult ; anterior side narrow, short ; ventral 

 margin sinuous ; umboes depressed, anterior ; 

 posterior side broader, square, biangular, broadly 

 truncated. 



LiNNiEus. Systema Naturaj. 

 Hiatella arctica, Lamarck. 

 Soleii minutus, Linnaeus. 

 Hiatella minuta, Turton. 

 Donax rhomboides, Desliayes. 



Hub. Arctic regions, British and North American 

 coasts. 



Species 2. Mus. ? (copied.) 



Saxicava Petitii. Sax. testa suhciuiciformi, sub- 



regidaiittr nigatd ; latere antico brevi, anguslo, 



margine ventrali pro/and!: sinuate, late hianti ; 



latere postico crpanso, rotnndatim oblique angulato, 



2>ost angulum lati; oblique tnincato ; margine dorsali 



recto. 

 Petit's Saxicava. Shell rather cuneiform, rather 



regularly wrinkled ; anterior side short, narrow ; 



ventral margin deeply sintious, broadly gaping ; 



posterior side expanded, roundly, obliquely 



angidar, broadly obliquely truncated behind the 



angle ; dorsal margin straight. 

 Deshayes. MS. Mus. Cum. in Brit. 



Uab. ? 



The wrinkles in this species are regidar and sharp. 



Species 3. (Mus. Brit.) 



Saxicava eugosa. Sax. testd tenuiusculd, rhomhoided, 

 lavigatd, ^ws/Zet vix angiilatd, leviter rngatd, 

 margine dorsali subarcuato ; latere antico brevis- 

 simo. 



The rdgose Saxicava. Shell ratlier thin, rhomboidal, 

 smooth, posteriorly scarcely angular, slightly 

 wrinkled ; dorsal margin a little arched ; anterior 

 side very short. 



LiNN^us (Mytilus). Systema Natural. 



Saxicaua Gallicana, Lamarck. 



^fl/a Byssifera, Fabricius. 



May, 1875. 



