Mr. H. Seeley on Cambridge Paleontology. 281 



Cymodocea antarctica. This plant, Professor Harvey informs me, 

 " occupies the same region of depth in Australia that Zostera 

 marina does here/' and is "very common everywhere in the 

 Laminarian zone, from just below low-water mark to perhaps 

 3-5 fathoms." He adds, " It harbours a number of Algse on its 

 stems — seldom on its leaves." The leaves afford a favourite 

 habitat to several of the Hydrozoa and Polyzoa, besides the 

 species which form the subject of this paper. 



EXPLANATION OF THE PLATES. 



Plate XIL 



Campanularia tincta, natural size and magnified. 



Plate XIIL 

 Lineolaria spinulosa, natural size and magnified. 



XXXIV. — Notes on Cambridge Paleontology. 

 By Harry Seeley. 



[Plate XL] 

 II. 8ome new Gasteropods from the Upper Greensand. 

 In the Cambridge Greensand, Gasteropods are rare — so rare, that 

 if one unaided were to search for a week, he would probably 

 gather nothing but a few specimens of one or two of the com- 

 moner species ; but, from the artificial abundance produced by 

 the numerous workings (extracting as they do every fossil from 

 whole miles of country), I have been able to examine nearly 

 2000 specimens. It is an extreme rarity to find the shell pre- 

 served, the specimens all occurring as internal moulds in phos- 

 phate of lime. I have not seen more than twenty specimens 

 having any trace of the shell, and in some of these it is con- 

 verted into the same substance as the cast. Many new species 

 besides those here described occur ; but, from the casts yet ob- 

 tained giving no indications of external characters, mention of 

 them is deferred for a future paper. 



For the figures, which have been made under my direction, 

 and chiefly from outline-sketches of my own, I am indebted to 

 my friend Mr. R. Farren. 



To the friends who assisted me in producing the paper on 

 Bivalves, and especially Prof. Sedgwick, I have again to offer 

 thanks for much kind help. 



Pteroceras globulatum. PI. XI. fig. 1. 

 Shell ventricose, ovately fusiform. Spire about one-third the 

 Ann. ^ Mag. N. Hist. Ser. 3. Vol. vii. 19 



