34 McMURRICH. [Vot. III. 
yellowish mesenterial filaments to show through, and was 
marked with six paler lines radiating from the mouth towards 
the bases of the tentacles of the first cycle. Peristome white, 
with the gonidia a more opaque white. 
The base is firmly adherent, apparently slightly larger in 
diameter than the column, measuring 2.5 cm., at least so it is 
in the preserved specimen, it being impossible to see either it 
or the column in the fresh specimens owing to the position of 
the tentacles. The column in these latter measured about 
2.9 cm. in height; in the preserved specimens the height was 
2 cm., and the diameter about the same. The surface of the 
column is thrown into transverse folds, and a close examination 
shows numerous minute tubercular elevations, produced, as 
sections show, by slender filiform processes of the mesoglcea. 
No special sphincter muscle is present, a circumstance which 
distinguishes the genus from Ophiodiscus, as already noted, but 
the general circular musculature of the column wall is fairly well 
developed, the mesogloea being raised into short unbranched 
processes which support it. The ectoderm consists principally 
of glandular cells, and measures about 0.817 mm. in thickness ; 
the mesogloea is thin, averaging only 0.04 mm. in thickness, 
though it varies somewhat; while the endoderm, containing 
numerous “ yellow cells,” is about 0.065 mm. in thickness. 
The disc is flat, and transverse sections show a fairly well- 
developed muscular layer, entirely ectodermal, however ; that is 
to say, it is arranged on elevations of the external surface of 
the mesogloea, and is not at all imbedded within its substance 
as in Ophiodiscus. The gonidial angles of the mouth are very 
distinct. The tentacles are marginal, simple, and cylindrical, 
hanging down over the column as in Ophiodiscus. They are 
long, measuring about 3 cm. in length, and are arranged in 
several cycles, their formula being apparently 6, 6, 12, 24, 48, 
96 (?). In structure they resemble closely the disc, there being 
a well-defined nerve layer (Pl. III, Fig. 13). The difference 
in the structure of the inner and outer surfaces of the basal 
portion of the tentacles which Hertwig describes in Ophzodiscus 
does not obtain here, although their marginal situation does 
entail some peculiarities. Thus, immediately at the base in 
some of the tentacles an endodermal musculature can be per- 
ceived as well as an ectodermal, which latter again is frequently 
