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



From the above records it is clear that Turritella communis generally 

 frequents a bottom of soft mud, or one in which there is a considerable 

 proportion of mud mixed with coarser deposits. Under these circum- 

 stances it seems rather strange that it should have been abundant near 

 the Eddystone on Ground IX., whilst it was absent on Ground XIII. 

 As will be seen from Table II., the bottom-deposits on these two grounds 

 are both coarse gravel, mixed in the one case (IX-, haul 94) with fine 

 sand, ill the other (XITL, haul 103) with mud; that is to say, the 

 percentage of silt in the latter case is very much greater than in 

 the former. We should have expected to find Turritella abundant on 

 the more muddy ground, but this is not the case. 



Aporrhais pes-pelecani. This mollusc was only twice obtained living, 

 once in haul 87 on the clean broken shell of Ground XVI., and once in 

 haul 55 on the coarse gravel mixed with fine sand of Ground X., both 

 on the west side of the Eddystone. Shells were frequently taken on 

 many other grounds, especially on the gravels to the west of the 

 Eddystone. These shells were sometimes occupied by hermit crabs, 

 sometimes by Fhascolion strombi. 



DisTiiiBUTioN. Geographical. Iceland, Finniark, British Coasts to Gibraltar and 

 Mediterranean (Jeffreys, Locard). 



Depth. 5 fathoms (Jeffreys) to 200 fathoms (Herdman, No. 40, Vol. VI., p. 80). 



BoUom-dejJOsit. Forbes and Hanley say that jipo7Th(tis pes-pelccani is found on gravelly 

 bottoms. Forbes {Brit. Assoc, 1850) gives seven records on coaise ground, two on sand, 

 one on sandy mud, and three on mud. Metzger gives four records from the Pommerania 

 dredgings, viz., on fine sand and shell, on sand, on nmddy sand, on shell and small 

 stones. Petersen found the s])ecies frequently all over the Kattegat, generally on the 

 mixed deposits (muddy sand or nniddy gravel), occasionally on pure sand, seldom on mud. 

 Iliancke (No. 39) found it at Heligoland only on muddy sand with some gravel. Herdman 

 found Aporrhais pcs-pelecani in Norway on mud and stones and on mud (200 fathoms). 

 In the Liverpool district Herdman records a very large number of living specimens 

 opjwsite Fleshwick Beach in 13 fathoms (No. 40, Vol. VIII., p. 18). In his subsequent 

 l)aper on the floor deposits of the Irish Sea (No. 44) the same author descril)es a sample of 

 the bottom-deposit of! Fleshwick Bay in 12 fathoms, which, I presume, refers to the spot 

 where these specimens were taken. This deposit consisted of slaty gravel mixed with shells, 

 and with fine material consisting of sand and a very fine "sand fioTir." Herdman also 

 records the sjjecies west of Fleshwick Bay, \ mile off shore, in 13 fathoms, on fine 

 sand and broken shell (No. 40, Vol. IX., p. 32). From these records it seems probable 

 that tlic distrilmtion of Aporrhais pc.s-2irhc(t)ii is not directly influenced by the nature of 

 tiie bottom deposit, and that the animal can live upon any kind of bottom, provided the 

 food supply and other conditions are satisfactory. It appears, however, that it is upon 

 muddy gravel that the species finds the conditions most suited to its needs and tliat it is 

 most abundant With reference to tlie peculiar shape of the shell of this animal, the 

 following suggestion, due to Mr. A. R. Hunt from his paper, " On the Influence of Wave 

 Currents on tlie Fauna inhabiting Sliallow Seas " (No. 64), is worth quoting in full :— " The 

 Gastropod Aporrliais pes pc/emni is a sluggish mollusc that frequents exposed areas of 

 sand a few fathoms below the surface of the water. Its long wing-like processes, jutting 

 out on one side of the shell, though allbrding the animal a broad base on which to rest, 

 apj)ear at first sight to be a source of danger in case it were overturned. They are in 

 reality self-acting pieces of mechanism that will, in tlic majority of instances, ensure tlie 

 mollusc being ultimately left in its normal posture sliould it encounter wave cuncnts 



