226 DORIDID^. 



their structure as the Nemertoid types among the Annelids. In 

 their embryonic state these lovely fragile Mollusks are supplied with 

 little, clear, spiral shells, and swim like Pteropods freely through 

 the water, being furnished, at this epoch of their lives, with two 

 head fins and a large frontal veil. As they grow, however, the shell 

 falls off, and tlie veil becomes modified, but is usually persistent in 

 the adult. They arc universally distributed throughout all seas. 



Family DORIDIDyE. 



Teeth, many in each cross series, sub-similar, inner often smaller. 

 Mantle-edge simple ; gills surrounding the vent, on the middle of 

 the hinder part of the back, in a common cavity. 



The Doridld(E form an assemblage of most attractive Nudibranchs, 

 which may be easily studied by placing them in glass reservoirs of 

 salt-water, as they are by no means shy, but extend their tentacles 

 and display their branchial plumes to great advantage. In this fam- 

 ily the gills are retractile into a common cavity, and the mantle is 

 very large, either entirely or almost covering and concealing the 

 foot. 



Oeiiiis POLYCERA, Cuvier. (1817.) 



Animal smooth or tuberculated. Tentacles clubbed and pecti- 

 nated, not retractile and without sheaths. Frontal veil consisting 

 of a series of tentaculiform appendages variable in number, often 

 extending along the borders of the mantle. Branchiae forming part 

 of a circle around the vent, encased by membranous laminee which 

 protect them. 



Polycera Lessonii. 



Plate XVIL Figs. 242-248. 



Animal yellowish-green, with tubercles tipped with sulphur yellow ; tentacles 

 short, obtuse, clubbed, with twelve to thirteen oblique laminfe ; veil small, about 

 twelve-lobed ; appendages to the branchiee spur-like, or obsoletely branched, 

 j'ellow. 



Polycera Lessonii, D'Orb. in Mag. de Zool. vii. .5, pi. 105 — Adams, Genera, ])1. 62, fig. 



9. — Alder and Hang. Nudib. Moll, in Ray See. fam. 1, pi. 24. — Chenu, Man.de 



Conch, i. 40.3, fio;. ,3040. 

 Polycera ciirina, Alder, in Ann. Nat. Hist. vi. 340, pi. 9, figs. 7-9 (young) (1841). 

 Polycera modesta, Loven, Index Moll. Scaad. 6 (1846). 



