266 MESSES. C. SHEAEER, W. DE MORGAN, AND H. M. FUCHS 



5. Inner Mewstone trawling ground (not often worked now). JE. esculentus 



common, E. acutus occasional. 20-23 fathoms. 12^-2 miles south of 

 Mewstone. Trawling is sometimes done farther out in deeper water in 

 25 fathoms. Nature of bottom — Vary variable, through dumping of 

 rubbish. 



6. Mewstone Ledge. 10-16 fathoms. E. esculentvs. In the region of the 



10 fathom line S. of the Mewstone. Occasional specimens of is', esculentua 

 are dredged about the Sound and ju.st outside the Breakwater, W. end. 



E. miliaris is obtained between tide-marks at the following places : — 



7. Reef S. of Wembury Church, Wembury Bay, E. 



8. Reef S. of Wembury Point, Wembury Bay, W. 



9. Reef S. of Renny Point. 



TO. Drake's Island, Plymouth Sound. 



11. Region of Kingsand Beach, Cawsand Bay, Plymouth Sound. Nature of 



ground — Usually very rocky, with numerous large loose boulders and 



stones. 



We have depended almost entirely for our supply of E. acutus and E. esculentus 

 on the first of these localities, the Looe-Eddystone grounds. 



Our supply of E. miliai-is has been derived, in most instances, from localities 7, 8, 

 and 11 ; but on occasions we have used material from all five localities where this 

 species is foiuid. During li)ll and 1912 a very considerable portion of our material 

 was obtained from localities 7 and 8, as localities 9, 10, and especially 11 were almost 

 fished out. 



From the account given of the grounds from which we have obtained our material 

 it will be seen that the distribution of E. esculentus and of E. acutus overlaps, while 

 the principal habitat of E. miliaris on which we have depended in this work is 

 difterent from that of the other two forms. A description of these three species of 

 Echinus and of their distribution is given by Mortensen (70) ; reference is made to 

 the conditions influencing the distribution of these two species by Allen (2). 



E. esculentus and E. acutus are species which are closely related to one another, 

 while E. miliaris stands apart from the other two. In general and in particular 

 characters E. miliaris can be sharply distinguished from the other forms, but the 

 characters on which the species E. esculentus and E. aculns are founded are not 

 nearly so distinctive. Moreover, these latter species are subject to a considerable 

 amount of variation, E. acutus in particular. E. acutus can be separated into three 

 varieties : Var. Norvegicus, var. Elemingii, and var. Mediterraneus. Var. 

 Norvegirus is found in the Northern European waters and in the Mediterranean. 

 Var. Flemingii is in Northern Europe only, and var. Mediterraneus in the Mediter- 

 ranean only. These varieties, however, are not definite and distinct from one 

 another, but all transitions can be found. The variety which occurs at Plymouth, 



