282 POLYZOA IffFUSDIBULATA. 



PLATE XLIX. FIG. 58. 

 Tubulipora palmata? S. V. Wood in Ann. and Mag. N. Hist. xiii. 14. 



Hab.On old bivalve shells from deep water dredged off San 

 Island by Mr. Hyndman, W. Thompson. Coast of Northumberland, 

 W.King. Dredged in from 110 to 140 fathoms off the Mull of 

 Galloway, E. Forbes. 



A fine species which creeps over the surface of bivalve shells in a 

 dendritical fashion, the branches a line or more in breadth, gradually 

 enlarging to the end so as to assume a clavate form ; and hence a 

 single branch, like that of the preceding, takes the figure of the tear 

 that has been arrested in its course. The polypidom is closely 

 adherent by an expanded base ; the branches are rounded or convex 

 superiorly ; the cells tubular, horizontal, semi-immersed, their septa 

 marked by pale lines, their parietes vitreous and granulous, the 

 aperture very little raised, oblique, and entire. These openings are 

 crowded at the extremity of the branches. 



This description is made from a specimen that had selected the outer 

 side of Tellina crassa for its site ; but another, which I think is re- 

 ferable to the species, on the inner and smooth surface of the Venus 

 ovata, is still more beautifully ramified, and the divisions are broader 

 and flatter, palmate at the ends, while the upper portion of the cells 

 is abruptly erect and free, as in the genuine Alectos. This is what 

 I suppose may be identical with the Tubulipora palmata of Mr. 

 Wood ; and I have sometimes thought that it might be a state of 

 Diastopora obelia. The student will occasionally find it not easy to 

 define the limits either of the genera or species in this family ; and I 

 would advise his examination to be limited to what appear to be 

 well developed and perfect specimens. 



On the outer surface of a Lima from the Isle of Man, sent to me 

 by Professor E. Forbes, there is an Alecto which I have scarce a 

 doubt is identical with the A. gracilis of Milne-Edwards. (Mem. p. 

 15, pi. 16, fig. 2.) The specimen, however, is not sufficiently per- 

 fect to admit of its being figured correctly. 



FAMILY CRISIAD^E. 

 Les CRISIES, Milne-Edwards Mem. p. 1-13. 



CHARACTER. Polypidoms phytoidal, jointed, dichotomously 

 branched ; the cells tubular, disposed in one or two series with 

 the circular apertures alternately looking to opposite sides. 



The true position of this family in its class was first perceived by 





