PERN A. 



Plate I. 



Genus PEE.NA, Lamarck. 



Tesla plamdata, fihro-laminaris, swbaqnivalvis, timbonihim 

 parvk, icepe term'maUhiis et aduncis. Cardo latiis, r,iar- 

 ffinalis, sidcia parallelk ligamentum excipientibus. 

 Lacuna pro bi/sso infra cardinis extremitateni posii- 

 cam. Ji/ipressio muscularis obliqua, distlncta. 

 Shell flat, fibro-laminar, nearly equivalve, umboes small, 

 often terminal and hooked. Hinge broad, marginal, 

 with parallel grooves receiving the ligament. Open- 

 ing for the byssus beneath the posterior extremity of 

 the hinge. Muscular impression oblique, distinct. 

 The shells assembled under the head of Perna are cha- 

 racterized by a special construction of the hinge, and like 

 the Aoicidrs, they attacli themselves by a tough, bristly 

 byssus. The hinge is in the form of a broad, marginal 

 plate cut across vvitli regular parallel grooves, and the in- 

 termediate ridges do not interlock with each other like 

 teeth, but press in contact, leaving the cavities between 

 them for the reception of the ligament. 



The shells of Perua have a strong affinity with those of 

 Malleus, in respect of their winged and laminar growth, 

 but they altogether differ in the arrangement of the hinge 

 and byssus. They are chiefly from the Eastern seas. A 

 few are from the West Indies and the Pacific islands. 



lamina: fimbriately scaled, umboes arched, hooked ; 

 dull-olive. 



Distinguished by a neat sculpture of flattened, over- 

 lapping, concentric frills of scales. 



Species 1. (Mus. Cuming.) 

 Perna lobata. Pern, icstd subquadratd, utrinqne con- 

 cavo-compressd, medio longitudinaliter lobutd, concn- 

 trice rudi laminatd ; pnrpicrascmte-albd. 

 The lobed Perna. Shell somewhat square, conoavely 

 compressed on each side, longitudinally lobed in the 

 middle, concentrically rudely laminated; purplish- 

 white. 



HnL. ? 



Of a contracted trapezoid form, with the laminee pressed 

 into a central lobe projecting longitudinally. 



Species 3. (Mus. Cuming.) 

 Perna Cumingii. Pern, tesld siiborbiculari, latere antico 

 basaliproducto, crassiusculd, concentrice rudi laminatd, 

 radiatim sulcata, laminis subfimbriatis ; violaceo-pur- 

 pnred,fusco tincld. 

 Cuming's Peuna. Shell somewhat orbicular, basal an- 

 terior side produced, rather thick, concentrically rudely 

 laminated, radiately grooved, laminte slightly frilled ; 

 violet-purple, tinged with brown. 

 Eab. Australia. 



This fine species has probably been confounded with 

 P. epMppium, but it is well distinguished by its radiating 

 grooves, which impart a frilled character to the concentric 

 lammse. 



Species 4. (Mus. Cuming.) 

 Perna nucleus. Pern, testa subquadrato-ovali, concen- 

 trice laminatd, laminis ad margineni striato-fimbriatis, 

 umbonibus arcuatis, aduncis ; sordide olivaced. 

 The hard-crusted Perna. Shell somewhat squarely 

 ovate, concentrically laminated, lamina; towards the 

 margin striately frilled, umboes arched, hooked; dull- 

 olive. 

 Lamarck, Anim. sans vert. vol. vii. p. 78. 



Hab. ? 



J.ess fimbriated than the preceding species, witii the base 

 broader, and the umboes still more sharpl 



hooked. 



Species 3. ( Mus. Cuming.) 



Perna pectinata. Pern, testd suborbiculari, pectlnatd, 

 tenuieuld, concentrice nitide laminatd, laminis fimbri- 

 ato-squamatis, imbonibus arcuatis, aduncis; sordide 

 olivaced. 



The pectinate Perna. Shell soracnhat orbicular, pec- 

 tinate, rather thin, concentrically neatly laminated. 



Species 5. (Mus. Cuming.) 

 Perna caudata. Pern, testd oblique ovatd, cramv.sculd, 



postice longitudinaliter lobata, radiatim striata ; lutes- 



cente-albn, purpurascente-striald. 

 The tailed Perna. Shell obliquely ovate, rather thick, 



posteriorly longitudinally lobed, radiately striated; 



yellowish-wldte, tinged with purple. 



Eab' ? 



Of a solid radiate growth, produced obliquely iuto a 

 rude, longitudinal lobe. 



November, 1858. 



