CLASS GASTROPODA 
269 
Ischnochiton magdalenensis Hinds, 1843 
Zoology of the Voyage of H. M. S. tSulphur, Molluscae, 54; PI. 19, fig. 1. 
Testa elongate-ovali, subelevata, medio pallida seu subcarnosa; valva- 
rum area laterali alaeformi radiatim corrugato-sulcata, transversim grosse 
lineata, madiata et antica longitudinaliter corrugato-sulcatis; ligamento 
scabriusculo. 
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 
alae or wings, are crossed by rude lines which appear to indicate periods 
of cessation of growth. The character of the coloring 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 Chitons on the west coast of 
America is very great, and they extend throughout its vast extent from 
Chile to a high northern latitude. They most usually abound in numbers, 
but are limited in their geographic range. Those of the coasts are nearly 
always distinct from those of the 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 particular locality by 
pointing out the species inhabiting it. (Hinds.) 
Type in ? Type locality, Magdalena Bay, Lower California. 
Range. Coos Bay, Oregon, to Magdalena Bay, Lower California. 
Ischnochiton sarcosus Dali, 1902 
Proceedings of the United States National Museum, 24:558. 
Chiton rather elongate, marbled with scarlet and white, paler mesially, 
rather low and not carinate; the girdle densely set with small, curved, 
smooth bristles of different sizes, dark red and white mixed; under side 
of the girdle chocolate color, and the interior of the valves flesh pink; 
dorsal angle somewhat more than 110°, the jugal region being rounded 
off; intermediate valves with prominent lateral areas hardly concentrically 
or radially sculptured, but finely punctate all over and more or less serrate 
near the girdle on the posterior margin; jugum not defined, central area 
of the valves longitudinally sculptured with low inosculating wrinkles 
which sometimes form diamond-shaped interstitial excavations; the whole 
sculpture has an obsolete appearance; anterior valve finely punctate, feebly 
concentrically sculptured; posterior valve the same, with a low subcentral 
[871] 
