Messrs. Alder and Hancock on new MoUusca, i261 



Fig. 8. StylovycTiia histrio, a peculiar phase of; the three globular ve si- 

 des subsequently coalesced into one large one, containing nu- 

 merous granules. 

 Fig. 9. Stylovychia Mytilus, showing the formation of embryos and the 



development of germinal globules. 

 Fig. 10. Urnula Epistylidis, growing on the stem of Episiylis plicatilis. 

 Fig. 11. Carchesium Aselli, with a large embr}onic vesicle : a, a detached 



embryo. 

 Fig. 12. Development of embrjos within embr3'onic vesicles in the same 



pnimalcule. 

 Fig. 13. Carchesium AselU strongly contracted, and with its ciliary disk 

 elongated and circumscribed by a constriction, making it resemble 

 an independent germ in course of growth. 

 Fig. 14. Zoothamnium nffine. The nucleus has broken up into numerous 

 minute globular corpuscles, collected within an outgrowth from 

 its side, terminated by an aperture. 

 Fig. 15. Conchophthirus Anodontce (Stein). 

 Fig. 16. Chasmatostoma reniforme. 

 Fig. 1/. Microthorax pusillus, ventral aspect. 

 Fig. 18. Microthorax sulcatus, ventral aspect, 

 Fig. 19. The same, dorsal aspect. 

 Fig. 20. Astylozoon fallax. 



XXV.' — Descriptions of a new Genus and some new Species of 

 Naked Mollusca. By Joshua Alder and Albany Hancock, 

 F.L.S. 



The following species of Nudibranchiate Mollusca have recently- 

 come under our notice, mostly through the kindness of our 

 friends, to whom our thanks are due for the liberal manner in 

 which they have communicated to us all specimens met with in 

 this department of natural history that were likely to prove new 

 or interesting. 



Family Dorididse. 



Doris iestudinaria, Risso, 



Doris tesiudinaria, Risso, Hist. Nat. de I'Europe Merid. vol. iv. p. 33, f. 15 ; 

 Phihppi, Enum. Moll. Sic. vol. ii. p. 7^' 



Body ovate or broadly elliptical, convex. Cloak large, of a 

 chestnut-colour, with indistinct pale-yellowish blotches towards 

 the sides, covered with smallish unequal tubercles, interspersed 

 with a few larger ones, with minute pale lines radiating from 

 them. Dorsal tentacles stout, yellowish, with fifteen to seven- 

 teen laminae, divided in front by a groove : oral tentacles linear. 

 Branchial plumes eight, tripinnate, forming an incomplete circle, 

 open behind, retractile within a large cavity. Underside of the 

 cloak orange- or lemon-coloured, spotted with reddish brown : 



