1918] Packard: Molluscan Fauna from San Francisco Bay 337 
This prevalent species has a general distribution within the middle 
and the lower divisions of the bay. It is characteristically a littoral 
species and would show a different distributional pattern from that 
given on plate 46, had the shores of the bay been investigated. 
Range.—Aleutian Islands, Alaska, to Monterey, California, with 
varieties ranging farther south. 
Thais lamellosa (Gmelin) var. septentrionalis (Reeve) 
Purpura septentrionalis Reeve (1846), pl. 10, fig. 50. 
Purpura crispata Chemnitz var. septentrionalia, Tryon (1880), p. 175, pl. 
’ 54, fig. 166; Wood and Raymond (1891), p. 57. 
This smooth form occurs abundantly in the region of San Francisco 
Bay. No attempt was made to separate it from the typical form as 
found in the Survey collections. 
Range.—Northward from Santa Barbara, California. 
Thais lamellosa (Gmelin) var. franciscana Dall 
Thais lamellosa (Gmelin) var. franciscana Dall (1915a), p. 565. 
Description.—This variety was described by Dall in the following words: 
“«Shell subfusiform, heavy, with a subeonie spire shorter than the aperture, 
laminae reduced to obsolete low imbrications or usually none; whorls flattened 
behind the shoulder; major spirals low, feeble, two on penultimate whorl, or 
more on the last whorl; minor spirals obsolete or none; aperture large, the outer 
lip flaring, umbilical chink usually distinet but closed.’’ 
This variety was not recognized until after the fauna had been 
determined. The variations within this species are illustrated on 
plate 40. Of the specimens figured, the following may be considered 
as belonging to this variety (pl. 40, figs. 5a and 5b). 
Range.—Known only from San Francisco Bay, which is the type 
locality for the species. 
Thais lima (Martyn) 
Purpura lima Martyn, Tryon (1880), p. 175, pl. 54, fig. 159; Wood and 
Raymond (1891), p. 57. 
Description.—Tryon (1880) described this species as follows: 
““Tts characteristic appearance is due to a considerable number of narrow, 
elevated revolving ribs, which are alternately larger. The shell is usually so 
thin that the external ribs form corresponding sulcations within the aperture. 
The suture is frequently channeled, color light brown, more or less banded and 
clouded with a deeper tint.’’ 
