47G ON THE FAUNA AND BOTTOM-DEPOSITS NEAR THE 30-FM. LINE 



From the above records it is clear that Spatangus purpureus lives 

 most frequently in gravel and shell gravel, or in coarse sand, though 

 it is not possible to judge from the great variety in the nomenclature 

 used by the various authors exactly what texture it is intended to 

 indicate. There seems no doubt, on the other hand, that the species 

 may, under certain circumstances, be taken on fine sand and mud, and 

 it will be important to notice in future what exactly are the conditions 

 under which this occurs. Especially it should be discovered, if possible, 

 whether such muddy or sandy grounds adjoin a coarse ground upon 

 which the species is abundant. 



Echinocardiurti cordatum. Chart V. Occasional specimens only of 

 this species have been taken, which may to some extent be due to the 

 fact that the trawl and not the dredge was generally used on fine sand 

 grounds. As the species can bury deeply in the sand, it would not be 

 likely to be captured in this way. 



Single specimens were, however, found on the inner and outer fine 

 sand trawling grounds (I. and II., hauls 51 and 104), on Ground VII., 

 haul 76 (sand), and on Ground XV., haul 97 (fine gravel). All the 

 specimens were of a dull white colour, and not bright yellow like those 



generally taken between tide-marks. 



Habits. The habits of this species are similar to those of Spatangus purpureus, except- 

 ing that it burrows in fine sand, and judging from the situations in winch it is found 

 between tide-marks, burrows to greater depths. 



Distribution. Geographical. Both sides of the Atlantic from Norway to Spain and 

 S. Carolina to Bahia. North Sea, Mediterranean {fide Bell, No. 7). 



Depth. 0-85 fathoms (Bell, Agassiz, No. 1). 



Bottom-deposit. Forbes states that the species abounds in sandy bays, and after storms 

 great numbers are cast on shore. All the authors (Mobius and Blltschli, Meissner and 

 Collin, Herdman, Petersen) record the species from fine sand and muddy sand only, 

 to which it is rigidly confined. 



The three heart urchins, Spatangus purpureus, Echmocardium 



cordatum, and Brissopsis lyrifera, form a good example of the fact 



that burrowing species are very much restricted by the texture of 



the deposit in which they dwell. Brissopsis lyrifera is as rigidly 



confined to mud as Echinocardium cordatum is to fine sand, whilst 



Spatang^is purpureus is almost invariably found upon deposits of 



coarser texture. This was recognised by Forbes when he proposed 



for the three genera the English names Bank-Urchin, Mud-Urchin, 



and Sand-Urchin (No. 22, p. 183). 



POLYCHAETA. 



[Nomenclature: — Generally that of Saint- Joseph (Nos. 101 and 102).] 



The Polychaetes of the earlier hauls were identified by Mr. T. V. 

 Hodgsou, those of the later ones by Professor Weldon. The responsi- 



