FROM THE EDDYSTONE GROUNDS TO START POINT. 501 



acv.leatum and C. tuherculatvm, and specimens are constantly taken, 

 which are very difficult to distinguish from one or other of these 

 forms. The fine sand in which Cardium echinatunt lives on the 

 Eddystone Grounds could hardly be described as fine, muddy sand, as 

 it contains a comparatively small quantity of silt, and it seems pro- 

 bable that the species lives in sand intermediate in texture between 

 that described by Hunt as occupied by 0. aculcatnm and by C. tvhcr- 

 cuiatum. The case is one of those in which it is extremely difficult 

 to decide whether we are dealing with one species, which grows in 

 a different manner according to the nature of the ground which it 

 occupies, or with three closely-allied species, each specially adapted 

 to sand of a particular texture. Such questions can only be settled 

 by experimental breeding of the species. 



Cardium norvegicum. The distribution of this species is shown on 

 Chart XIV. and should be conti-asted with that of Cardium cchinatum 

 (fresh shells). The species is most abundant on Ground XIV., which 

 is a fine gravel ground. It extends on to the grounds immediately 

 surrounding this, but is not abundant on the coarse gravel mixed with 

 fine sand, one living one only being taken on Ground IX. Living 

 specimens were also taken on Ground IV,, which in other features 

 indicates the influence of fine gravel as well as sand. 



DisTKiBUTlON. Geocjraj)hicaJ . Finiuark, British Coasts to Mediterranean, Azores 

 (Locard, No. 69), Madeira, and Canaries (JetTreys, No. 55). 



Depth. 10 or 15 to 1200 fatlionis (Talisman, No. 69). 



Bottom-deiwsit. Forbes and Hanley state that the species occurs on sandy or gravelly 

 hottoms ; Forbes (No. 24, Brit. Assoc, 1850) records it from shell; Gwyn JeflVeys says 

 that it is found on sandy and nnllipore bottoms. Metzger (No. 77) gives three records 

 from the Pommcrauia drcdgings, viz., on stony ground, on fine sand with small balls 

 of mud, and on fine sand with pieties of shell. From the Liverpool district the species 

 is recorded from small gravel and shells (No. 40, Vol. VI., p. 110). Petersen (No. 95) 

 says that in the Kattegat the species seems to prefer sand to soft, mixed gi-ounds. 



From the above records it is, I think, clear that this species is found 

 especially on coarse ground, such as broken shell and nullipore ground. 

 C. norvegicum, which has a perfectly smooth shell, may therefore be 

 regarded as completing the series presented by C. aculcatnm, with long 

 spines, living in fine muddy sand; C. cchinatum, with stout spines, 

 living in fine sand ; and C. tiiberculatum, with tubercles, living in 

 "hard" sand. 



Montacuta suhstriata. This mollusc was invariably found attached 

 to the spines of Spcdaiigus purimrcus, tiie position in which it is 

 commonly found. Gwyn Jeffreys states that it sometimes occurs also 

 on Eckinucardiuni cordatiim and on other sea-urchins. 

 DisiKiiiUTiON. Finniark to Mediterraiiciin. 



KcUia suborhicu/ariii. Table VI. This species, taken on Grounds VII., 

 IX., X., and XiV., west of the Kddystoiie, was guiu'rally found living 



