ORDERS AND FAMILIES. 



Filibranehiata. (PELECYPODA.) Plates i. and ii. Nos. 9 to 29. 



. Shell irregularly oyster-shaped, having no teeth, and being 

 attached to rocks and stones by a calcified byssus which passes 

 through a large hole near the hinge. Anomia, g, 10. 



ARCADE. Shell with valves equal ; hinge long with many serrate teeth ; 

 muscular impressions nearly equal ; foot large, bent, and grooved ; 

 mantle edge with composite eyes. Area, n to 15 ; Pectunculus, 16 ; 

 Limopsis, 17, 18. 



^E. Shell with valves equal, but inequilateral ; beaks incurved ; 

 anterior muscular impression small, posterior impression large ; byssus 

 well developed ; ligament long and narrow and in a groove. Mytilus, 

 ig to 23 ; Crenella, 24, 25 ; Modiolaria, 26 to 29. 



Opisthobranchiata. (GASTROPODA.) Plates xxx. to xxxiii. 

 Nos. 550 to 611. 



ASCOGLOSSA. Plate xxxi. Nos. 586 to 590. 



ELYSIID.E. Body depressed, head rather elevated ; no branchiae ; no 

 shell ; sides of body dilated into two large wings. Elysia, 588. 



.^:. Body depressed; no branchiae; no shell; cerata in several 

 rows. Hermcea, 586 ; Alderia, 587. 



LIMAPONTIID^E. Body slug-like; no branchiae or other appendages; no 

 shell. Limapontia, 589 ; Actceonia, 590. 



NUDIBRANCHIATA. Plates xxxi., xxxii. Nos. 591 to 6n. 



Body slug-like ; head with tentacles ; dorsal area with rows 

 of cerata usually containing sting cells. JEolis, 591 ; Embktonia, 592 ; 

 Fiona, 593; Proctonotus, 594; Antiopa, 595; Hero, 596. 



DENDRONOTID^;. Body slug-like, rather compressed; two rows of 

 arborescent cerata ; no tentacles ; pointed margin, with arborescent 

 papillae. Dendronotus, 599. 



. Branchiae of a circle or semicircle of pinnate leaves, united at 

 base. Doris, 603. 



DOTONID^. Body slug-like ; two rows of cerata, each ceras surrounded 

 by a ring of tubercles. Doto, 598. 



GONIODORID^:. Body oval; branchiae multifoliate, and in the shape of a 

 horseshoe. Goniodoris, 609; Ancttla,6io; Idalia, 611. 



LOMANOTID.E. Body slug-like; one row of small cerata; no tentacles. 

 Lomanotus, 597. 



PLEUROPHYLLIDIID^. Body covered by arched shield, with lateral angles 

 prolonged ; mantle pale reddish brown, with small black specks. 

 Pleurophyllidia, 601. 



POLYCERID/E. Body slug-like ; branchiae not retractile ; tentacles simple, 

 usually surrounding the posterior end. Polycera, 604 ; JEgirus, 605 ; 

 Triopa, 606 ; Thecacera, 607 ; Crimora, 608. 



