Length 70µ; greatest diameter 48µ.

Tintinnopsis davidoffi Daday. Fig. 48.

The shell is large, elongated, and provided with a considerable spine. The chitin of the shell is covered with silicious particles of diverse size. The internal structures were not observed.

Length of shell and spine 230µ; diameter of the oral aperture 54µ.


Fig. 48.—Tintinnopsis davidoffi.
[ ENLARGE ]

The variations of these species are considerable, and as the internal structures, such as the nucleus, are essential in fixing their systematic position, I place them as above, provisionally, and until further observations can be made.

Key to families of Hypotrichida.
a. Peristome indistinct; cilia on ventral surface uniform and not differentiated into cirri Family Peritromidæ
One genus, *[Peritromus]
b. Peristome more or less indistinct; cilia reduced to a few rows on the ventral surface; anal and frontal cirri present Family [Oxytrichidæ]
c. Cilia entirely reduced; frontal and anal cirri present or reduced; macronucleus band-formed or spherical Family [Euplotidæ]
d. Peristome reduced to left edge and does not reach over the anterior margin Family Aspidiscidæ
One genus, *[Aspidisca]
* Presence at Woods Hole indicated by asterisk.