LIMNOCODIUM (e RASPEDACUSTES) SOWERBII. 
351 
On Limnocodium [Grasp edacustes) Soweebii, a new Tracho- 
MEDUSA inhahiting Eresh Water. By E. Bay LA^fKESTEE^ 
M.A., E.E.S. With Plates XXX and XXXI. 
At the meeting of the Eoyal Society on June 17th, and in 
^ Nature^ of that date, I described in the following terms a re- 
markable Medusa which I had received a few days before : 
On Thursday last, June 10th, Mr. Sowerby, the Secretary 
of the Botanical Society of London, observed in the tank in the 
water-lily house in BegenPs Park some peculiar organisms, of 
which he was kind enough to place a large number at my dis- 
posal on the following Monday. 
The organism proves to be an adult Medusa, belonging to 
the order Trachomedusae, and the family Petasidae, of HaeckeFs 
system. It comes nearest among described genera to Eritz 
Miiller^s imperfectly known Aglauropsis, from the coast of 
Brazil. 
** The most obviously interesting point about the form under 
notice is that it occurs in great abundance in perfectly fresh 
water, at a temperature of 90° E. Hitherto no Medusa of any 
order has been detected in fresh water.^ 
'' It is exceedingly difficult to trace the introduction of this 
animal into the tank in the BegenPs Park, since no plants have 
been recently added to the lily-house, and the water is run off 
every year. Probably a few specimens were last year, or the 
year before, present in the tank, and have only this year multi- 
plied in sufficient abundance to attract attention. Clearly the 
Medusa is a tropical species, since it flourishes in water of this 
high temperature (90° E.) 
" Mr. Sowerby has observed the Medusa feeding on Daphnia, 
which abounds in the water with it. 
The present form will have to be placed in a new genus, for 
which I propose the name Craspedacustes.^ 
It presents the common characters of the Trachomedusm (as 
distinguished from the Narcomedusae) in having its genital sacs 
or gonads placed in the course of the radial canals. It agrees 
with both Narcomedusae and Trachomedusae in having endoder- 
mal otocysts — and further presents the solid tentacles with car- 
tilaginoid axes, the centripetal travelling of the tentacles, the 
tentacle-rivets (Mantelspangen), the thickened marginal ring to 
the disc (Nesselring) observed in many Trachomedusae. 
* Except, perhaps, some estuarine forms (Crambcssa and others). 
^ Kpmo-TTtSaKovoTTjc, One wlio liears by means of the KpacnnZoVf or 
velum. 
