54 ZOOLOGY OF THE VOYAGE OF THE SULPHUR. 



Family — Chiton ace^;. 



Chiton. Linnaeus. 



219. Chiton magdalenensis, (Plate XIX. fig. 1.) Testa elongate ovali, subelevata, medio 

 pallida seu subcarnosa ; valvarum area, laterali alseformi radiatim corrugato-sulcata, transversim 

 grosse lineata, mediant et antica longitudinaliter corrugato-sulcatis ; ligaraento scabriusculo. 



Inhab. Bay of Magdalena, California. In considerable numbers on the 

 rocks. 



In shape elongated, and, the middle valves being scarcely of greater breadth 

 than the others, with the margins somewhat linear. The lateral spaces, and 

 which with much propriety and convenience might be called alee or wings, are 

 crossed by rude lines which appear to indicate periods of cessation of growth. 

 The character of the colouring of the dorsal ridge is disposed to vary. In an 

 individual of this species the phenomenon occurred of the existence of nine valves ; 

 and though Chitons are not indisposed to diminish the number by one or more, it 

 seems far less frequent that they should increase them, as this is the only instance 

 within my experience. 



The number of species of Chiton on the West coast of America is very great, 

 and they extend throughout its vast extent from Chili to a high northern latitude. 

 Without doubt they occur farther in both directions, but I only speak of our own 

 experience. They most usually abound in numbers, but are limited in their 

 geographic range. Those of the coasts are nearly always distinct from those of 

 deep water. So very prone are they to restrict themselves to narrow portions of 

 the coast, that it would be exceedingly easy to convey a close idea of any parti- 

 cular locality by pointing out the species inhabiting it. Some of the southern 

 species are rather disposed to extend their range, but the great mass are exces- 

 sively local. 



Family — Neritace^:. 



Neritina. Lamarck. 



220. Neritina (Nerita) Reclusiana, Le Guillon, Revue Zool. Nov. 1841. 

 Nerita Keraudreni, Le Guillon, 1. c. Nov. 1841. 

 Neritina Armstrongiana, Hinds, Ann. Nat. Hist. vol. x. p. 82. 



