176 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



filiform tip; not longer than ventral rami with their setae. Palpi in preserved 

 specimens short, conical, pointed, with subterminal black zone. 



Dorsum very broadly exposed between the elytra, which are unusually small, 

 broadly reniform or orbicular, and either entirely immaculate or more rarely 

 with a central black spot and flecks of black, or with a black border on 

 posterior edge. Dorsum marked with numerous irregular, transverse bands, 

 lines, and streaks of burnt sienna; the pigment massed in a broad, solid fillet 

 on somites eight and nine. The rest of the body unpigmented. 



Parapodia (fig. 51) small and numerous, short; dorsal ramus rudimentary, 

 achaetous (or rarely with a few small setae); ventral ramus stout, bearing two 

 kinds of setae: (1) a supra-acicular fascicle of blunt, slightly curved ones (fig. 

 516); and (2) an infra-acicular series of hooked setae (fig. 51a), similar to those 

 of P. pulchra and P. fragilis; about 20 setae in all. Ventral cirrus present, 

 small and fusiform. 



Number of somites, 67 to 74; elytra 31 to 35 pairs, extending to extreme 

 posterior end of body. 



Measurements. — Length of full grown specimen, 57 mm.; greatest width, 

 7 mm. 



Habitat. — Northern portion of California Coast to Puget 

 Sound. Commensal with Glyphis asfiera and probably 

 other Fissurellidae, nestling under the mantle. Also with 

 Cryftochiton stelleri, in the branchial groove. 



I have a little hesitation in referring the species above- 

 described to Baird's Halosydna lordi, although his de- 

 scription of the latter, based upon abundant material col- 

 lected by J. K. Lord at Macaulay's Point, Vancouver 

 Island, does not in all respects agree with the specimens at 

 my command. For example, he describes the dorsal setae 

 as " stout, smooth, somewhat curved as they approach the 

 point, enlarged and flattened and uncinate at the point; 

 those of ventral or lower division a little more slender, 

 slightly enlarged near the point, which is straight, blunt, 

 and striated across." My specimens are for the most part 

 destitute of dorsal setae, and have two different forms of 

 setae in the ventral ramus, neither of which agrees with 

 Baird's description. The host mentioned by Baird is Fis- 

 surella cratitia. All my specimens from the Puget Sound 

 region were in the mantle cavity of Glyfihis asflera; those 

 from Cape Mendocino are stated on the label to occur 

 under the mantle of " Fissurella,'" but what species I do 

 not know. Very probably these came from Glyftkis asfiera 



