72 DR. A. GUNTHER ON THE ZOOLOGICAL [Feb. 6, 
18. ARCA, sp. 
Two small shells, probably the young of aa larger species, seem 
most nearly allied to 4. gradata, Brod. & Sowb.; they are rather 
more finely reticulated than is usual with that species, but in form, 
and the position of the umbones, they agree very well. 
B. Terrestrial Species. 
‘ 
19. Butimus nux, Broderip. 
The specimens of this species collected by Commander Cookson 
are very coarsely striated, and much darker in colour than those de- 
scribed by Broderip. They are striped longitudinally with a mixture 
of slate-colour and brown, with here and there some pale streaks ; 
and some specimens have a distinct pale band around the middle of 
the body-whorl; and the four apical whorls are bluish black. 
This species is considerably variable in form, some examples being 
much more elongate than others. 
The following measurements show how great is the variation in 
length. One shell is 20 millims. long and 10 in diameter, and 
another very short one has a length of only 16 millims. and yet is 
the same width as the longer specimen. 
20. Butimus unirasciatus, Sowerby. 
21. BuLimus ESCHARIFERUS, Sowerby. 
This species is quoted by Reeve as having been found at Chatham 
Island by Darwin. The Charles-Island shells are considerably 
larger than those from the above locality, and also coarser in sculp- 
ture, some of them displaying spiral granose or rugose striation as in 
B. rugulosus of Sowerby, from the same islands ; and, indeed, they 
appear to be an intermediate variety or connecting link between the 
two species, both as regards size and sculpture. The largest speci- 
men measures 19 millims. in length, and 73 in width. 
22. SuccINEA BETTI, sp. nov. (Plate XI. fig. 8.) 
Testa ovata, superne aliquanto acuta, tenuissima, diaphana, flavo- 
cornea, versus apicem rubescens, irregulariter arcuatim striatula, 
nitens ; anfractus 3, penultimus parvus convexus, ultimus max- 
imus, inflatus ; apertura ovata, superne angustata vix obliqua ; 
columella obliqua, parum arcuata, tenuissime callosa; peristoma 
simplex regulariier arcuatum. 
Long. 13 millim., diam. maxima 8, aperture longit. 10 millim., 
diam. 53. 
Var. Testa brevior. 
This species is most nearly allied to S. rubicunda Pfeiffer, which 
was described as coming from the island of Masafuera, off the coast 
of Chili. From it the present species differs in consisting of half a 
whorl more. This difference is quite apparent when the spires of 
the two species are regarded with the mouth of the shell towards the 
eye. ‘The penultimate and apical whorls of the Galapagos species 
