382 BALANID.E. 



some one may, perhaps, succeed in grouping several of these forms as 

 species ; but I am sure he ought not to attempt it without possessing 

 a very large suite of specimens, or without the great advantage of com- 

 paring some two or three of the forms, fresh in their native site. 



Species dubice. — Under Pyrgoma, I have stated that though Chenu, 

 in his 'Illust. Conch.,' has given beautiful external figures of the 

 shells, imbedded in the coral, yet from the want of details on the oper- 

 cular valves and on the structure of the shell, I cannot recognise his 

 species. So it, likewise, is with Creusia. Chenu gives the following 

 new species ; C. radiata, multistriata, decorata, and striata. The C. 

 madreporai'iim, I suspect to be the Pyrgoma milleporce of this work, 

 as there stated. The C. grandis no doubt is the P. grande of this 

 work, the Nohia grandis of Sowerby. The name Creusia Childreni is 

 given by Dr. Gray, without description or figure, in the ' Annals of 

 Philosophy,' vol. 10, new series, 1825. 



n 



7. Genus — Chelonobia. PI. 14: PL 15, fig. 1. 



Ciielonobia. Leach. Journal de Physique, torn. 85, (1817). 

 Coronula. Lamarck. Animaux sans Vertebres, 1818. 



— Ranzani. Memoire di Storia Naturale, 1S20. 



— Be Blainville. Diet, des Sciences Naturelles. 

 Astkolepas. J. E. Gray. (Klein) Annals of Philosophy, (new 



series), vol. 10, (1825). 



Compartments extremely thick, six ; but one of them, the 

 rostrum, internally is composed of three rudimentary com- 

 partjj/ents, united together : basis membranous : scuta narrow, 

 united to the terga by a horny articular ridge. 



Distribution, throughout the tropical, and warmer temperate seas of the whole 

 world; attached to turtles, Crustacea, or smooth gasteropod molluscs. 



This is a distinct and well-defined genus. Several 

 authors have confounded it with Coronula, but this has 

 been owing to an entire misapprehension of the structure 

 of the shell in the two genera. In Coronula, the parictes 

 are very thin, and are so deeply folded as to appear like 

 rays or septa connecting the outside of the shell (the ex- 



