532 Mr. W.S. Macteay’s Anatomical Observations 
forming an internal tunic corresponding to the outer covering 
or test, and provided like it with two openings, as in having 
branchiæ which occupy all, or at least part of the membrana- 
ceous cavity formed by the internal sides of the mantle. 
From 
the Acrita they differ in having distinct nervous and generative 
systems, while their intestinal canal is provided with. two open- 
ings both internal. 
Shis osculant group may be divided as follows : 
Aberrant group? 
1. TETHYA. 
Or such Tunicata as have 
their mantle adhering to 
the envelope or test only 
at their orifices; — their 
branchiæ regular, consti- 
tuting the sides of the re- 
spiratory cavity; and their 
branchial orifice surround- 
ed by a membranaceous 
ring, which in general is 
supplied with tentacula, 
ss in PORN... 
Normal group? 
2, THALIDA. 
Or such Tunicata as have 
their mantle adhering 
every where: to the enve- 
lope; their branchiæ irre- 
gular, consisting of two fo- 
liated processes attached 
to the sides of the thorax ; 
and their branchial orifice 
merely provided with a 
TW = 
sree re ow 
à 
TUN ICATA. 
Families, 
(1. ASCIDIDZ*, 
2. BOTRYLLIDA, 
3. LuciDp x. 
Lucies Sav. 
< 
4. BIPHORIDA. 
L5. PERE SE 
Tethyes simples Sav. 
Teth. composées Sav. 
Animals. Generic Types. 
Simple and fixed, having 
their orifices externally 
itregular. 4... 2, 4 ASCIDIA. 
Compound and fixed, hav- 
ing their orifices exter- 
nally regular ,...,,,. POLYCLINUM. 
Compound and floating, 
having .their branchial 
cavity open at the two 
extremities... ., sers PYROBOMA. 
Aggregated in their young 
state, and floating .... SALPA. 
* De Blainville considers that the Pyura Moline makes the passage from the simple 
to the compound Tethya; that is, from the Ascidide to the Boiryllide. Savigny 
shows 
