4 ZOOLOGY OF THE VOYAGE OF THE SULPHUE. 



not regard as attributable to their fecundity, but rather as the circumstance which 

 has enabled them to effect their diffusion. 



Scarcely an American shell is seen in the Pacific. On leaving the American 

 coast, and touching at the Marquesas, a few individuals of abundant Indian species 

 are noticed, as Purpura persica, Ricinula digitata, Conus marmoreus, Cyprcea carneola, 

 Solarium perspectivum, Cythercea gibbia, and others, but in considerable scarcity. 

 Proceeding towards the westward, additional Indian species appear at every 

 group, and the conchology becomes gradually more rich and abundant. 



I was somewhat surprised to find, that there was a marked difference in the 

 shells inhabiting the interior and the exterior of coral islands. Within, the water 

 of the lagoon is always tranquil, and scarcely ripples on the shores, which are 

 formed of small fragments of coral or coral sand ; without, an agitated sea beats 

 unceasingly on a barrier of hard coral rock. In both situations, a platform exists, 

 which at low-water is left bare, but at high-water is covered from a few inches to 

 about two feet. Among the shells confined to the interior are Tellina scobinata, 

 Cythercea gibbia, Pecten pallium, Pedum spondyloideum, Conus betidinus, C. textilis, 

 C. geographies, and some others, with several of the well-known Pacific species of 

 Mitra, Cyprcea, Pteroceras, and Terebra. Those of the exterior are more particu- 

 larly several species of Ricimda, Purpura persica, Conus hebrceus, C. sponsalis, 

 C.vermiculatus, Turbo setosus, and Cypricardiarostrata. The three cones abound 

 in myriads on the outer platform ; but C. hebrceus is also found in the lagoon, exces- 

 sively rare, and in unusually fine condition ; whilst without, it is equally abun- 

 dant, but quite dwarf. The shells of the interior are remarkable for their thin 

 epidermis, delicacy of colour, and for the very severe fractures they have sustained 

 during some period of their existence, and the reparation of which often originated 

 some strange distortions. 



The terrestrial gasteropodes have also their partialities. The influence of a 

 moist climate is well-known, and need not be dwelt upon ; at the Sandwich 

 Islands and New Ireland, Ave acknowledged its effects in the great variety of 

 species and the multitudes of individuals. And of the numerous circumstances 

 under which they are found, I shall only mention that certain kinds are prone to 

 particular elevations, beyond which they do not seem inclined to exist. 



These are but a few brief remarks on a subject not without interest, and which 

 might be considerably extended. In the following pages such species only are 

 introduced as are regarded as hitherto undescribed, or where some observations 

 are elicited. From the American portion of our voyage, a number of shells have, 

 within the last few years, been described ; but comparatively so few, that it rather 

 pointed the way, than deprived our researches of originality. Notwithstanding 

 the "fievre conchologique," which, with some truth a French writer has remarked, 



