OB ANIMALS WITHOUT BLOOD. 219 



The valves of Pinna are rough, according to Aristotle, 

 but not ribbed,* and, secured by means of a byssus, they 

 grow up erect in the sand or mud.t He also says that 

 a small crab, the Pinnoteres, or Pinnophylax (guardian of 

 the pinna) , lives within the shell. I It is well known that 

 a small crab lives in the gills and mantle of several lamelli- 

 branchs, such as, for example, Pinna squamosa, of the 

 Mediterranean. 



Some of Aristotle s most interesting statements about 

 the Kteis (pecten), relating to its sense organs and mode of 

 progression, have been discussed already in Chapters xii. and 

 xiii. respectively. He says also, speaking of its valves, that 

 they are ribbed, and that the large kinds of pecten have one 

 valve flat. It is true that the common edible pecten and 

 some others have the left valve flat or nearly so. 



The solens are sufficiently clearly described by Aristotle. 

 He says that their valves are smooth, || and that they live in 

 sandy shores, remaining in one place, but not fixed in it, for 

 they can withdraw themselves into the sand, when alarmed. 1f 

 His suggestion that solens can see has been discussed in 

 Chapter xii. 



Most of the molluscs described by Aristotle are marine, 

 but he also clearly refers to various snails of the genus Helix, 

 which he calls by the name Kochlias. He says that the 

 terrestrial Kochliai hybernate, and, during the period of 

 hibernation, have an operculurn.** He also says that these 

 Kochliai are devoured by pigs and partridges. 1 1 



Sea-urchins and star-fishes were included by Aristotle 

 among his Ostrakoderma, but were considered by him to be 

 exceptional forms. Speaking of sea-urchins (Echinoi), he 

 says that there are several kinds, one having large and edible 

 ova, another, called Echinometra, which is the largest of the 

 sea-urchins, and a third kind having large and hard spines, 

 and living in many fathoms of water. J 1 He also refers to 

 two deep-sea and rare forms, viz., Spatangos and Bryttos, 

 and some white Echinoi, of longer form than the others, and 

 having somewhat small and soft spines; these white Echinoi 

 were found near Torona, in Macedonia. 



It is not easy to identify the above-mentioned echino- 



* H. A. iv. c. 4, s. 3. 



f Ibid. v. c. 13, s. 8. J Ibid. v. c. 13, ss. 8 and 9. 



Ibid. iv. c. 4, ss. 3 and 12. || Ibid. iv. c. 4, s. 3. 



II Ibid. iv. c. 8, s. 18, v. c. 13, BS. 8 and 10. 

 ** Ibid. viii. c. 16, s. 1. f f Ibid. ix. c. 25, s. 3. 



H Ibid. iv. c. 5, ss, 1 and 2, Ibid. iv. c. 5, ss. 2 and 3. 



