70 J. D. MACDONALD ON METAMORPHOSIS OF GASTEROPODA. 
I next observed a stout little shell, much resembling a Macgillivrayia in form, but 
having the spire more minute and sharply marked, and the whorls beset with epidermic 
spines, disposed in close spiral lines. The microscopic examination of the animal gave 
unmistakeable proof of its being a Banella, the lingual dentition agreeing, at least gene- 
rically, with my figures and specimens. The rachidian plates of Banella are boomerang- 
shaped, with the convexity in front, bearing a recurved angular process divided into sharp 
denticles. There is often also a small tooth on the posterior border of each arm, near its 
outer extremity. The uncini of the first series are sickle- shaped and serrulated, with a 
tooth on the inner side of the base, and those of the second and third claw-shaped, 
simple. 
On .examining the operculum, which in Banella is so very remarkable, exhibiting three 
successive stages of growth, I found that it was quite of the same character, only that it had 
but yet attained the second stage. Finally, on comparing the whole operculum, and the 
little shell, respectively, with the nucleus of the operculum, and the apex of the shell of 
an adult Banella obtained on the reefs, I could detect no points of difference, even with 
magnifying powers ; the conclusion, therefore, is irresistible, that the one is but the young 
state of the other. 
The young of Triton was also determined by the same mode of analysis, and I have 
been able to confirm my former conviction, that Cheletropis belonged to the Muricida* 
and that certain other pelagic shells, which I also figured and described, were referrible to 
the Naticidce and Strombidce respectively. 
Of Macgillivrayia I obtained a new species, closely resembling that named M. echinata 
by Mr. A. Adams, only that the spines, which are disposed in a single row on the dorsum 
of the whorls, were perfectly straight and not "recurved;" and the later additions made 
to the outer lip extended as a thin lamina over the whorls towards the apex of the shell, 
a condition which I have also discovered in the young of Triton, and which affords one 
amongst many reasons for placing Dolium and Malea (to which the several species of 
Macgillivrayia appear to belong) with Triton and Banella in one natural family, culling 
them from amongst the very numerous and heterogeneous genera of the two families, 
Strombidce and Buccinidw, in which they are at present to be found. All these animals 
have a protractile proboscis with a septiserial lingual ribbon, partaking of the characters 
of that of Banella, as above described. A pair of lateral oral plates, in general composed 
of indurated rhomboidal cells, is also invariably present ; and if these particulars cannot 
be affirmed of a genus selected for this family from some fancied resemblance of its shell- 
characters, nothing is more certain than that some other natural family will be minus a 
member. 
I obtained once more the little Gasteropod which I was unfortunate enough to name 
Jasonilla, it having previously, according to Mr. Adams, received no less than three titles, 
viz. Broicnia (D'Orb.), Echinospira (Krohn), and Calcarella (Souleyet), though the ana- 
tomy of the animal remained unknown. I am now fully satisfied that the true shell is 
developed within the outer cartilaginous case which rejoices in the above synonyms, and 
that it is merely the young state of Lamellaria (a Gasteropod with a concealed spiral shell), 
of which we obtained a living specimen at the Cato Tleef. 
