PODOCORYNE AREOLATA. 353 



hydroid published by Wagner. As may be easily expected, no notice is taken in that account 

 of certain points which arc now found to be necessary for a satisfactory diagnosis, and the species 

 has not been met with by any one since it was found by Wagner, many years ago, on the shores 

 of the Adriatic. 



4. PODOCOEYNE AREOLATA, AlcUr, sp. 



Hydractinia AREOLATA, — Aider, Suppl. Catal., p. 1, pi. ix, figs. 1 — 4. 

 Rhizocline AREOLATA, — Allmau, Ann. Nat. Hist, for May, 1864. 

 PoDocoRYNE AREOLATA, — Hiucks, BHt. Hydr. Zooph., p. 33, pi. vi, fig. 1. 



TROPHOSOME. — Common basis of the colony set witli " simple linear spines in 

 irregular^ groups." Htdranths attaining a height of about one tenth of an inch, 

 sub-cylindrical, with from six to ten tentacles. 



GONOSOME. — GoNOPiiORES sessile on the common basal expansion, large, globular, 

 or slightly pear-slia])ed. Radial tentacles of medusa rather short, three still shorter 

 tentacles developed in each inter-radial space of the margin ; manubrium with each of 

 its four lips supporting a tuft of thread-cells. 



Colour. — Hydranths white ; radiating canals of medusa golden yellow. 



Habitat. — On dead univalve shells. 



Localities. — Coast of Durham, Mr. Alder; Shetland, Rev. A. ■\I. Norman. 



Some years ago, when attempting a revision of the genera of tubularian hydi'oids, I saw that 

 it was impossible to retain the hydroid named Hydractinia areolata by Alder in the genus to 

 which this naturalist had assigned it, and, not being able to find a place for it in any published 

 genus, I constituted for it a new one under the name of RMzocIine. 



I do not, however, desire to insist upon the retention of the genus Rhizocliiie. It is highly 

 probable that the basal expansion in jMr. Alder's hydroid resembles that of Hydractinia, and 

 that its true natiu'e had been overlooked when he described it as " consisting of a solid chitinous 

 expansion, from which arise simple chitinous spines." I have further satisfied myself that there 

 is no essential difference between the common base of Hydractinia and that of Podocoryne ; and 

 then the only distinction between Alder's hydroid and the admitted forms of Podocoryne will be 

 found in the position of the gonophores, which in the former arc sessile on the common base. 

 This can hardly amount to a generic difference, though its very exceptional character might lead 

 us to expect such a diflcrcnce in other parts of the hydroid. We have accordingly — though as 



^ In Alder's description the word is " regular," but this is plainly a misprint. 



