VAN NAME: SIMPLE ASCIDIANS. 
479 
scattered irregular hair-like processes, most of which are very short. 
The apertures are not raised on tubes or papillae, and are difficult 
to discern from the exterior. The branchial aperture is well forward 
at the anterior end of the body, the atrial some distance back. Test 
in the preserved specimens yellowish gray, somewhat transparent when 
Text-flg. 6.^ Caesira septentrionalis (Traiistedt). X 2.2. 
the foreign bodies incrusting it are removed, and of a tough, cartilagi- 
nous consistency. 
Musculature of the mantle strong. It corresponds exactly with 
that described in European specimens by Hartmeyer (1903). From 
the bases of the siphons (if that term can be applied to such low pro- 
jections) strong muscle bands radiate upon the surface of the body 
extending some distance except upon the area between the siphons. 
A strong ring muscle lies externally upon these radial muscles at the 
base of each siphon. Along each side of the region of the endostyle, 
and transversely or somewhat obliquely placed, are spindle-shaped 
bands, w'hich are more conspicuous on the left side than on the right 
and form in places more or less noticeable longitudinal rows. 
Oral tentacles stout, with broad membranes, but very scantily 
branched. There are about a dozen large tentacles probably repre- 
senting two orders, and some branched tentacles of a smaller (third) 
order in the intervals. Still smaller tentacles also occur, but are 
rather few, and the usual scheme of arrangement is not very strictly 
adhered to. The branching of the larger tentacles is to some extent 
irregularly bipinnate, those of the third order are only once pinnate; 
the tips of the stout short branchlets are rounded and often slightly 
enlarged. 
Dorsal lamina with a smooth straight rather thick margin; endo- 
stvle unusuallv stout. 
