CHAP, in.] THE CR VISES OF THE ' PORCUPINE.' 117 



marked differences as distinct species, after having 

 gone over some thousands of them — some brought 

 up ia nearly every haul of the dredge from Fseroe to 

 Gibraltar — I am inclined to suspect that they may 

 be all varieties of Echinus flemingii. I have already 

 alluded to the countless myriads in which the 

 small form of E. norvegicus, D. and K., 15 mm. in 

 diameter, swarms on the ' Haaf ' fishing banks. 

 These little urchins are mature so far as the develop- 

 ment of their generative products is concerned ; and I 

 suspect from the abundance of three sizes, that they 

 attain their full size in two years and a half or three 

 years; but in colouring, in sculpture, and in the 

 form of the pedicellarise, I do not see any character to 

 distinguish them from a form four times the size, 

 common in deep water off the coast of Ireland; 

 nor, again, can I distinguish these last by any definite 

 character which one would regard as of specific value 

 from the shallow water form of Echinus flemingii, as 

 large as the ordinary varieties of E. sphcera. 



The Shetland variety of Equus cahallus is certainly 

 not more than one-fourth the size of an ordinary 

 London dray-horse, and I do not know that there is 

 any good reason why there should not be a pony 

 form of an urchin as well as of a horse. 



Professor Alexander Agassiz^ has discovered that 

 the Plorida species of Echinocyamus is nothing 

 more than the young of a common Elorida clypeas- 

 troid, Stolonoclypus prostratus, Ag., and he sug- 

 gests the possibility of our Echnocyamus angulosiis, 

 Leske, being one of these stunted ' pony ' varieties, 

 or undeveloped young, either of the American Stolo- 



' Bulletin of tlie Museum of Comparative Zoology, No. 9, p. 291. 



