314 Proceedings of the Royal Physical Society. 



Fig. 4. Sacculina triangularis ; external skin and eoriurn reflected : a, external 

 skin covered internally by the corium ; i, ovigerous lamellae. 



Fig. 5. Ovigerous sac, stowing the anterior and posterior folds which embrace 

 the internal ovaries. 



Fig. 6. Mass of ova from the ovigerous lamellae. 



Fig. 7. Greatly magnified view of one of the vesicles, drawn from a fresh 

 specimen : a, the duct of the vesicle ; c, the structure found in the 

 interior of the vesicle ; Z>, the horny substance found at the com- 

 mencement of the duct. 



Fig. 8. The same organ as fig. 7, drawn from a specimen preserved in alcohol : 

 a, the convoluted duct ; b, the horny process. 



Fig. 9. The structure found in the interior of the vesicle, removed. 



Fig. 10. Sacculina carcini, with no ovigerous lamellae, nat. size : b, the 

 peduncle ; b f , intestine of crab ; c, ovario-branchial orifice. 



Fig. 11. Sacculina triangularis, nat. size. (Same references as in fig. 10.) 



Fig. 12. S. carcini distended with ova. 



Fig. 13. Posterior view of fig. 12 ; d, horny attachment of peduncle ; k, pro- 

 longed portion of the same. 

 Fig. 14. A group of S. triangularis. 

 Fig. 15. S. inflata (after Leuckart). 

 Fig. 16. Enlarged view of the vesicles of S. carcini. 



II. Observations on British Zoophytes. 1. Hydractinia areolata, n. sp. 

 2. Atractylis arenosa, n. sp. (Plate XIV.) By Joshua Alder, Esq. 

 Communicated by T. Strethill Wright, M.D. 



1. Hydractinia areolata, n. sp. Plate XIV., figs. 1-4. 



Polypary encrusting, consisting of a solid chitinous ex- 

 pansion, from which arise simple linear spines in irregular 

 groups, leaving areolar spaces between them. Polyps 

 naked, small, white, columnar, slightly enlarging above, 

 and terminating in a conical mouth, below which is a single 

 circle of from six to ten linear tentacles, appearing of dif- 

 ferent lengths from their varying contractility. Gono- 

 phores (reproductive organs) sessile on the chitinous base, 

 large, globular, or slightly pear-shaped, containing each a 

 single medusoid. Height of polyp about T V th inch. 



Medusoid with a moderately deep subglobose umbrella, 

 having four golden-yellow radiating canals, at the bulbous 

 bases of which, on the margin of the umbrella, are four 

 rather short tentacles ; four shorter ones alternate with 

 them ; and intermediate between these are eight others, 

 almost tubercular. The peduncle is rather long and co- 



