238 TETHYDE. TETHYZ. 
ORDO I. TETHYD. 
The mantle adheres merely to the branchial and anal aper- 
tures. The branchie or gills are equally broad, and line the 
interior surface of the cavity of respiration. The branchial 
aperture is furnished either with a membranaceous denticulated 
ring or with a circle of filaments. 
FAMILY I. TETHY &. 
Tethyz, Savigny. 
The apertures with indistinct rays. The body sessile. 
Genus 1. AScIpIA. 
GEOYPIYM, Aristotelis. 
Ascidia, Baster, Linné, Cuvier, Sc. 
The body is cylindric or oval, sessile, generally covered with 
a coriaceous integument, produced above into two cylindric 
tubes, the one branchial, the other anal: the apertures of the 
tubes are undulated, or notched with indistinct rays. 
* 
1, Ascip1a Britannica. Tab. XI. fig. 1. 
The integument smooth, cylindric, testaceous, transparent ; 
its apertures undulated, ornamented with carnation spots. 
Height three inches ; breadth one inch. 
Inhabits the British seas ; is common on all our coasts in 
deep water. 
2, ASCIDIA PAPILLOSA. 
Tethys coriacea, Bohad. Mar. 130. t. x. f. 1. 
Ascidia papillosa, Linn. Syst. Nat. xii. 1087. no. 287; Cuv. 
Meém. sur. ? Anat. des Moll. t. u. f. 2. 
The integument testaceous, smooth and papillated ; its aper- 
