456 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.49. 



Section AGRIODESMA DaU. 



Agriodesma Ball, Proc. U. S. Nat. Mus., vol. 37, No. 1704, p. 284, Nov. 1909. 

 Type. — Entodesma saxicola Baird. 



ENTODESMA (AGRIODESMA) SAXICOLA Balrd. 



Lyonsia saxicola Baird, Proc. Zool. Soc. London, for 1863, p. 70. Type locality, 

 Vancouver Island. 



Distribution. — Nestling like Saxicava in rock crevices from Una- 

 laska, Aleutian Islands, eastward and southward to San Pedro, 

 California. Cat. No. 88876, IJ.S.N.M. 



This enormous rude species, sometimes reaching nearly 6 inches in 

 length, is by all odds the largest species of the family. The coarse 

 horny periostracum m drying always cracks the calcareous portion 

 of the valves and I have never seen a perfect specimen except when 

 preserved in alcohol. Its nestling habit results in an infinite variety 

 of distorsion. The lithodesma is very large and strong and is inserted 

 obliquely below the dorsal margin. The varietal name cylindracea 

 Carpenter was given to specimens which had grown to fit borings of 

 LithopJiaga. 



ENTODESMA (AGRIODESMA) SCAMMONI Dall. 



Entodesma scammoni Dall, Amer. Journ. Conch., vol. 7, pt. 2, p. 142, pi. 16, 

 fig. 3, 1871. 



Distribution. — Type locality, Port Simpson, British Columbia 

 (Scammon). Cat. No. 213713, U.S.N.M. 



This species differs from aU the others in its brilliantly pearly 

 interior, its oval shape, and its permanently adherent periostracum 

 without radiating lines. Only the original specimens collected in 

 1865 have so far been obtained. 



Genus MYTILIMERIA Conrad. 



Mytilimeria Conrad, Journ. Acad. Nat. Sci. Phila., vol. 7, p. 246, pi. 19, fig. 5, 

 1837. Type. — M. nuttallii Conrad. 



MYTILIMERIA NUTTALLII Conrad. 



Distribution. — Vancouver Island and south to San Diego, Cahfornia. 

 Cat. No. 74234, U.S.N.M. 



It is by no means certain that this genus is properly placed here, 

 despite its conchological characters. The little that is known of its 

 anatomy points rather in the direction of Verticordia. The animal 

 lives surrounded by a mass of spongy texture which has been referred 

 to as ''sponge," but it is possible that the substance is a consolidated 

 mucous exudation secreted by the animal itself. Further researches 

 are needed to settle these questions. 



