GASTEROPODES. 289 
4. Trrronta contrera—The Pine Tritonia.—Plate XLI. Figs. 12, 13. 
I have sometimes conjectured that the subject of this paragraph 
might be a /usus nature ; but not being entitled, without better evidence, 
to presume that it is so, a place is reserved for it here. 
Length five lines ; general form and aspect resembling the Tritonia 
pinnatifida ; tentacula two, long, retractile, within dilatable sockets ; a 
dark speck is obscurely seen, behind the root of each, by the microscope. 
Six pair of branchie : two, being a pair of stumps, rise from the 
back. The first pair is very low, the second disproportionately large, the 
third pair not half their length or thickness, the fourth and fifth dimi- 
nishing, and the stumps denoting incipient organization. Besides all 
these, a large central branchial tuft or cluster is situate on the back, 
between the two branchise of the third pair. The structure of the tufts 
bears some resemblance to a pine-apple, the prominences somewhat higher 
comparatively. Colour of the animal dingy white, the tufts darkly 
speckled. 
The motion of this animal, when crawling, appeared unsteady, from 
the disproportion between the size of the tufts e nd of the body. Under 
the microscope the latter resembled ovoidal prominences ; the central 
one, at the summit, larger than the rest. Five series, or stages, compose 
the tuft. 
Only one specimen of this animal occurred, which survived nine 
weeks. 
Puate XL. 
Fic. 12. Tritonia conifera. 
13. A tuft, magnified. 
Note.—A. species, somewhat analogous in the formation of the 
pranchix, is referred to in the Melibea fragilis —Forbes' Malacologia 
Monensis, p. 41, Plate I, figs. 4, 9. 
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