M D I L A. 



Plate I. 



Genus MODIOLA, Lamarck: 



Testa ohlonga, aquivalvis, plm minus ventricosa, umbombus 

 patris, tumidiusculis, haud terminalibus, latere antico 

 sape expanso, postico arcuato, coniracto. Cardo line- 

 aris, ligamento marginali, subinieriio. Impresuo mus- 

 cularis compodta, sublateralis. 



Shell obloug, equivalve, more or less veutricose, witli the 

 iimboes small, rather swollen, not terminal, anterior 

 side often expanded, posterior arched, contracted. 

 Hinge linear, with the ligament marginal and par- 

 tiaUy internal. Muscular impression compound, sub- 

 lateral. 



The typical distinction between Mylilm and Modiola 

 consists in the latter having a lighter and more cylindri- 

 cally oblong shell, with the umboes rounder and not ter- 

 minal, in consequence of the posterior extremity of the 

 sheU protruding beyond them. This generic form' is, how- 

 ever, subject to more decided variation than MytilL, and 

 excellent subdivisions have been established under the 

 names Modiolarca, Crenella or Lanistim. 



Modiola is somewhat more numerous in species than 

 Mytilus, omitting even the Lithodond, which form an ex- 

 tremely characteristic group, and they are often beauti- 

 fully painted while less sculptin-ed. Their range of habi- 

 tation is equally widely spread. 



dMlus. It is iiL-atJy ornamented throughout with raised 

 thread-like stria;, but they exist apparently only in the 

 epidermis. 



Species 1. (Mus. Cuming.) 



Modiola Philippinarum. Mod. testa oblongo-trapezi- 

 formi, ventricosa, aniice sniexpansd, conceutrice deme 

 filo-striald ; pnllide castanm, liiteo-radiatd. 



The Philippine Modiola. Shell obloi>g-trapeziform, 

 ventricose, anteriorly somewhat expanded, concentri- 

 cally densely thread-striated ; light-chestnut, yellow- 

 rayed. 



Hanley, lleccnt Bivalve Shells, p. 235. 



Ilab. Philippine Islands. 



This interesting species, from the Philippine Islands, 

 luLs very much the typical form of the European M. mo- 



Species 2. (Mus. Cuming.) 

 Modiola modiolus. Mod. testa oblongd, subtrapeziformi, 

 versus umbones ventricosa, laevigata vet obsolete corru- 

 gato-striatd ; intense castaned. 

 The bushel Modiola. Shell oblong, somewhat trape- 

 ziform, ventricose towards the umboes, smooth or 

 obsoletely wrinkle-striated ; dark-chestnut. 

 Mytilus modiolus, Linn»us, Syst. Nat. p. U5S. 

 Mytilus icmbilicatus, Pennant. 

 Mytilus curtus. Pennant. 

 Mytilus curvirosfraius. Da Costa. 

 Modiola Papuana, Lamarck. 

 Modiola m.odiolus, Turton. 

 Modiola vulgaris, Fleming. 

 Ihb. North Atlantic shores of Europe and America. 



This, the largest species of the genus, well known on our 

 own shores, is common throughout the whole of Northern 

 Europe and America. 



Species 3. (Mus. Cuming.) 



Modiola vagina. Mod. testa cylindraceo-oblonyd, recta, 

 lenui, aubdepressd, concentrice dense subiilisdmi striata, 

 radiatim linear i-striatu et obsolete undato-corrugatd] 

 nltente-castanea. 



The sheath Modiola. Shell cyliudrically oblong, 

 straight, thm, rather depressed, concentrically densely 

 very fiiwly striated, radiately linearly striated and 

 obsoletely wave-wrinkled ; shining-chestnut. 



Lamakck, Anim. sans vert. vol. vii. p. 22. 

 Mytilus areuarius, Rumphius ? 



IM. Philippine Islands ; Cuming. 



A peculiarly straight, cyliudrically oblong species, of 



slight substance, with a delicate silky surface of a shinin.r- 



chestnut colour. " '^ 



January, 1858. 



