TEREBRATULA. 35 
transmitted for the nourishment of the body through tubes 
and variously-shaped walled canals or cavities, though they be 
neither typical arteries or veins; we go further, and believe 
that in many of these beings a blood circulation may be as 
effective through a single walled canal as by a more complex 
arrangement, and thus receive the~ necessary aération, which 
in most of the lower Invertebrata is probably cutaneous and 
effected by endosmose, and that in those animals in which the 
ambient element can only be admitted imto visceral cavities, it 
is oxygenated by exosmose. 
ACEPHALA PALLIOBRANCHIATA. 
TEREBRATULIDA. 
Having already mentioned most of the incidents of this 
family, I have only to add, that it consists of three genera, 
Hypothyris, Terebratula, and Argiope. None of the animals 
or the shells have occurred on the Devon coasts, except the 
Argiope cistellula, and that only im a dried state. 
HYPOTHYRIS, Phillips. 
H. psirracea, Chemnitz. 
H. psittacea, Brit. Moll. 11. p. 346, pl. 57. f.1, 2, 3. 
We can only refer to the first vol. p. 150, of the ‘ Zoological 
Transactions,’ for Professor Owen’s account of this animal. 
The shells of this genus are never punctated. A very doubt- 
ful British species. 
TEREBRATULA, Bruguiére. 
T. CAPUT SERPENTIS, Linnzeus. 
T. caput serpentis, Brit. Moll. ii. p. 353, pl. 56. f. 1, 2, 3, 4. 
The valves of this genus are always punctated, and particu- 
larly so in this species; it is taken plentifwlly on the Scotch 
D2 
