JIJLLUSCA. 631 



Ixxvii. fig. 10. Somewhat square, compressed ; undulateil, and transversely 

 striated ; and with a series of lamellated longitudinal scales ; greenish on 

 the outside and pearlaceous within. Ten or twelve inches Ions,'. Inhabits 

 the Indian oiean. 



Avicula Anglica. — The English Avicula. Plate Ixxvii. fig. 11. Winfj 

 moderate, obliquely curved ; yellowish fawn-coloured, willi dark reddisii- 

 brown blotches; inside pearlaceous. One iuch and a fourth long^. Inhabits 

 the Devonshire coast. 



Malleus a/ba.— The White Malleus. Plate Ixxvii. fig. 12. Trilobate ; 

 oase of the lateral lobe prolonged, without a sinus, the base and the pit for 

 the ligament not distinct ; white, with transverse undulatiims. Four inches 

 long. Inhabits the Australiau seas. 



Peina Ephippium. — The Saddle Perna. Plate Ixxvii. fig. 13. Compressed, 

 suborbicular ; left valve produced, the margins acute; purplish-brown on 

 the outside, and pearly within. Four inches long. Inhabits the Indian 

 seas. 



Crenatuta Myiiloides. — The Bluscle-Shaped Crenatula. Plate Ixxvii. fig. 

 14. Oblong-ovate, oblique ; the base acute ; violet coloured, with obscure 

 radiations. Inhabits the Red sea. 



Pinna Ingens. — The Huge Pinna. Plate Ix.xvii. fig. 15. Nearly triangu. 

 lar, horn-coloured, smooth, with distant foliations ; striated on one side, 

 with rough scaly wrinkles on the broader end. Twelve inches long. In. 

 liabits the coast of Britain. 



M'ltilus edulis. — The Edible Mussel. Plate Ix.'cvii. fig. 16. Oblong-oval, 

 nearly smooth, pointed and slightly carinated at the beak, truncated on one 

 side, and dilated on the other ; covered with an olivaceous epidermis ; be- 

 neath which it is radiated with blue or purple; internal margin blue, the 

 concave part white. Two to three inches long. Inhabits the British seas. 



Modiola discors. — The Discordant Modiola. Plate Ixxvii. fig. 17. Oblong, 

 oval, very convex, produced and narrower at the anterior end ; longitudin- 

 ally striated on both sides, and transversely in the middle ; outside green ; 

 inside white or pale pink ; margin crenulated at the base ; the beak oblique. 

 One half inch long. Inhabits the British seas. 



Hippopus Maculatus. — The Spotted Hippopus. Plate Ixxvii. fig. 18. 

 Transversely ovate, ventricose, with scaly ribs, and reddish purple spots; 

 lanule cordated, heart shaped, and oblique ; the margins very deeply creuu. 

 lated. Eight inches broad. Inhabits the Indian seas. 



Tridacna gigas, — The Giant Tridacna. Plate Ixxvii. fig. 21. Large, white, 

 transversely ovate ; with broad ribs, provided with vaulted scales ; the 

 posterior slope heart-shaped and gaping. Two feet six inches long, and 

 four feet six inches broad, the largest of all known shells ; sometimes 

 weighing above fire hundred pounds. Inhabits the Indian ocean. 



ORDER II.— DIMYAIRA. 



Contains Seventy-one Genera, 



I. Etheria; 2. Chama; 3. Diceras; 4. Iridiim : .■>. Auadorita; 6. Hyria; 

 7. Unio; 8. Castalia; 9. Trigonia; 10. Nucula ; 11. iVctunculus ; 12. Areaj 



