90 VARIETIES OBTAINED AT ONE LOCALITY. 
VARIETIES OBTAINED AT ONE LOocALITY BY A SINGLE Haut oF 
THE DREDGE. 
Captain Horsfall, of the steamship ‘ Canopus,” plying between 
Liverpool and Alexandria, calling at Malta and Gibraltar, placed — 
all the shells brought up from a rich spot of dredging ground in a 
match-box, and gave the box with its contents to me. It is 
labelled, “‘ Off Malta.” 
There were quite a large number of rare and interesting genera 
almost peculiar to the Mediterranean Sea, such as Typhis Sowerbyi, 
Broderip ; Murex cristatus, Brocchi, var. Blainvillei; Raphitoma 
gracilis and linearis, Montague, costata, Donovan, and var. 
coarctata ; Erato levis, Donovan; Marginella (Gibberula) clandes- 
tina, Brong., and miliaria, Linn., &. Among the bivalves were 
Kellia suborbicularis, Montg. ; Woodia digitaria, Linn. ; Mytilicardia 
aculeata, Poli, &c. There were also two or three different species 
of Brachiopods, among them Crania, Rostrata, Hoen, &c. The most 
interesting, as well as the most curious part of the collection 
obtained, however, is a series of varieties belonging to the genus 
Nassa, illustrating a phase in the history of these shells totally at 
variance with all my previously conceived ideas regarding the 
distribution of what are termed species and varieties. I had 
obtained a fine series of varieties of the Nassa incrassata, Miiller, 
as well as a numerous collection of its variety, Nassa glaberrima, 
Chemnitz, from the different stations at which the most distinct 
forms had been collected, the impression existing in my mind being 
that the changes that had taken place in these varieties had been 
produced by local variation, such as temperature, food, &c., but 
when the varieties were obtained, as in the above instance, by 
Captain Horsfall, upon the same bank and in the same water, no 
such governing influences could have been instrumental in producing 
them. The first is a narrow variety of the N. prismatica, Brocchi, 
with oblique ribs, showing an affinity with the N. miga, Adamson, 
from Senegal. So many of the Mediterranean Shells are represented 
by African forms that we cease to regard the circumstances as any- 
