276 Playfair Mc Murrich. 



Genus Metridiuiu Oken, 1816. 

 Mefridiinae with the cinclides scattered; columii wall witli a collar. 



18. '^ MetridiutH parvuluin n, sj). 



No. 123. Coquimbo. 4 — 19 fathoms. 9 specimens. 

 252a. Calbuco. 1 specimen. 



508. Calbuco. 1 specimen. 



The individuals representing- this species were all small except 

 the Single specimen, No. 252a, from Calbuco, and were apparently 

 young-. The specimens from Coquimbo were taken upon a muddy 

 bottom, adhering" to Shells of Pecfen pnrpuratus and No. 252 a was 

 seated upon a piece of coralline. 



The base in all the specimens is larger than the column (Fig. 66 1, 

 which, in the majority, is distinctly constricted a short distance 

 above the limbus. Above the constriction the column is cylindrical 

 Ol* tapers slightly to the margin, between which and the bases of 

 the outermost tentacles is a relatively broad interval. At the 

 margin the mesogloea is somewhat thickened, but above the wall 

 is thinner than elsewhere, making it seem probable that in the 

 expanded condition the margin formed a collar situated some distance 

 below the tentacles, as in Mefridmm dianilms. The periphery of 

 the disc showed, however, no indications of the lobation charactefistic 

 of that species. The column wall was practically smooth, except 

 for some faint ridges; cinclides were observed in sections, but they 

 could not be recognized with certainty on the surface, although in 

 the specimen from Calbuco an acontium protruded from the column 

 wall half way between the limbus and the margin. 



The tentacles are more or less exposed in all the specimens 

 and are somewhat entacmaeous. The inner ones may be described 

 as moderately long and all are thin-walled and blunt at the apex. 

 In one specimen, of which serial sections were made, there were 

 forty-eight tentacles. but in other individuals there were probably 

 fewer, judging from the number of mesenteries present. The disc 

 and mouth were completely concealed by the tentacles in all the 

 specimens. 



The height of the column in the small specimens was only 3.0 

 to 4.0 mm and the diameter at the base 6.0—6.5 mm. The largei- 

 specimen from Calbuco measured 7 mm in height and had a basal 



