134 REPORT — 1856. 



Additional Observations which could not be conveniently embodied in the 

 foregoing Table. 



Saxicava arctica, Lin. — Absent from no district witliin the range of my re- 

 searches, but is much more frequent and larger in tiie northern than in 

 the southern latitudes. The large solid variety, now living only in the 

 Arctic seas, is found dead (fossil ?) in deep water on the coasts of 

 Scotland. 



Gastrochaiua modiolina. Lam. ; Gastrochisena cuneiforrais, Lam. — Not ha- 

 ving been able to detect any specific difference between the British spe- 

 cimens and those from the south of Europe, 1 treat them as identical. 

 In the Canaries the specimens are smaller and inhabit greater depths 

 than in other localities. 



Ceratisoleu legumen, Lin. — Is of much smaller size in southern localities ; 

 frequent at Malaga, but not eastward in the Mediterranean. 



Donax anatinus, Lam. — I have dredged abundantly from 15 fathoms on the 

 Dogger Bank, a remarkable exception from its ordinary habitat. 



Donax venustus, Poli. — Is closely allied to Donax a7iatinus, of which it 

 takes the place at Lisbon, Mogador and in the Mediterranean ; in latter 

 associated with D. truncidtis. 



Tellina solidula, Pulleney. — Is reported to be frequent in the Mediterranean, 

 but I have never met with it south of Britain, 



Mactra subtruncata, Da Costa. — There are two distinct varieties (? species), 

 the one larger, solid and strongly rudely striated concentrically, is sub- 

 littoral, and most abundant on some of the Scottish shores ; the other, 

 small, smooth and thin, is more generally distributed, both as regards 

 depth and climate. 



Venus striatula, Don. — On the Mediterranean coasts of Spain and to the 

 southward, it is comparatively rare and confined to deep water ; in the 

 British seas it frequents all the zones of depth. 



Astarte arctica. Gray. — A valve obtained from west of Zetland, 50 fathoms, 

 by Prof. E. Forbes and myself, and recorded in the ' British Mollusca,' 

 is in my possession, and I have every reason to believe it to be fossil. 

 The reasons which induce me to believe that this species is not an actual 

 inhabitant of the British seas are, that it is a shallow-water species, 

 very gregarious, and not met with on the coast of Norway, south of 

 the Arctic Circle. 



Astarte compressa, Mont. — Subject to great variety in form, size, &c. I be- 

 lieve A. Banksii to be only a variety of this species. 



Kellia suborbicularis, Mont. — I incline to think that there are two species in- 

 cluded under this name, if not, they are well-murked varieties ; the one 

 smaller, more orbicular and more pellucid ; the other much larger, more 

 elliptical and, when fully grown, less transparent. It is the last which 

 is found imbedded in very fine mud contained in dead bivalves. 



Cardium edule, Lin. — Varies greatly in size, form, number of ribs, &c. 

 Near Tunis a narrow neck of land divides the bay from a shallow salt- 

 water lake, at the head of which the city of Tunis is situated ; on the one 

 side of tiiis neck of land (that facing the bay) all the specimens of Car- 

 dium edule were strong, triangular, and with few ribs, while on the side 

 towards the lake, they were thinner, wider and much more numerously 

 ribbed. The northern varieties attain the largest size. 



Modiola Petagnae, Scacchi — In shallow water in the harbour of Carthagena, 



1 



