14 Couthouy's New Species of Mollusca 
denizens of our vicinity, it seems very singular, both that 
they should have eluded the observation of our natural- 
ists so long, and should now have entirely disappeared. 
In dismissing this subject, I cannot but express my 
regret at being compelled to offer to the Society so 
much of hypothesis and so few facts relative to the 
habits and structure of these animals. The necessity of 
obeying (in Natural History especially) the * carpe 
diem ” was never more fully illustrated than in the pre- 
sent case. My avocations, the lateness of the season 
(November) when I first met with the Eolis, and, as I 
then thought, the certainty of a more favorable time for 
examination on the ensuing spring, all combined to pre- 
vent my pursuing it farther at that season, and I have 
now only unavailing regrets left me that I did not perse- 
vere. I would again express the hope that some mem- 
ber of this Society will profit by my neglect, and com- 
plete what I have so imperfectly begun. 
Trironta RevNorpsmn.. 
Plate II. figs. 1, 2, 3, 4. 
Ti — a postice attenuato, papilloso seu verrucoso, 
rubro-fi maculis albidis notato; tentaculis duabus serratis, 
vaginulis lacinalatis retractilibus; branchiis arboreis, utrinque quinis, 
posticé gradatim minuentibus; ore corrugato, branchiis vel ramulis 
branchiiformibus senis instructo, papillisque numerosis circumdato. 
Medium length three and a half inches. i 
Hab. tide waters of Charles River, Mass., at the 
Bathing House, Cragie’s Bridge. 
My own collection. 
Cabinets of Bost. Soc. Nat. Hist., New York Lyceum 
Nat. Hist., John C. Jay, M. D., New York 
