TEREBKATULA. 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 aeration, 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 into visceral cavities, it 

 is oxygenated by exosmose. 



ACEPHALA PALLIOBRANCHIATA. 



TEUEBEATULID^l. 



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 in a dried state. 



HYPOTHYRIS, Phillips. 



H. PSITTACEA, Chemnitz. 



H. psittacea, Brit. Moll. ii. p. 346, pi. 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, Bruguiere. 



T. CAPUT SERPENTIS, Linnaeus. 



T. caput serpentis, Brit. Moll. ii. p. 353, pi. 56. f. 1, 2, 3, 4. 



The valves of this genus are always punctated, and particu- 

 larly so in this species ; it is taken plentifully on the Scotch 



D2 



