188 K. p. TOMES ON MADEEPOEAEIA 



mens of Thamnastrcea, both of Great-Oolite and Inferior-Oolite 

 species, for comparison, but did not in any instance meet with an 

 example having a single row of calices surrounded by long septal 

 costae. I may confidently state that Tricydoseris Umax is not the 

 young form of any English species of Thamnastrcea, though I cannot 

 at present be sure that it is not the young of an Oroseris. However, 

 as I know of no «pecies of the latter genus to which it can be re- 

 ferred, I must, for the present at any rate, regard it as a distinct 

 genus, but will omit no opportunity of investigating more fully the 

 several periods of growth of the last-named genus. 



MiCEOSoLENA EXCELSA, M.-Edw. & Haimc. 



The specimens from which MM. Milne-Edwards and Haime took 

 their description of this species were found in the Great Oolite near 

 Bath, and formed part of Mr. Walton's collection. Some years since 

 I was favoured by that gentleman with specimens from Earley Down, 

 and was at the same time informed by him that all his specimens 

 had been taken from that locahty. During the present year (1884) 

 I was conducted to the spot by the Eev. H. H. Winwood, when I 

 made the following note of its occurrence there. 



Although fragments may be found scattered all through the coral- 

 bed, it is only at two very restricted and not very distant spots that 

 this species is abundant. It is there found in a softish white layer 

 which is overlain by a bed of hard stone. To the under side of the 

 latter the coral appears to be attached by a rather small base, from 

 which it ramifies in every direction downwards, and forms a thick 

 rounded bush which attains to a height of as much as a foot and a 

 half. The peculiar position of these bush-shaped masses, bottom 

 upwards, would seem to indicate that the whole of the beds had 

 tumbled over and reversed the position of the corals, a conclusion 

 not however borne out by the presence, in place, of the regularly 

 bedded compact Bathstone immediately beneath, which was at one 

 time worked at that place, and is still well exposed. 



I have examined several specimens of this species from the rail- 

 way-cutting near Stonesfield, which are worthy of mention. They 

 are attached to worn specimens of Thamnastra^a Lyelli, are small 

 in size, and have a pyramidal or subconical form, with a large 

 apical calice, and an irregular ring of smaller ones near the base, 

 just as in the genus Ge7iabacia. At this period of their growth 

 they might be referred to an attached species of that genus, such as 

 Genahacia Sancti-mihieli of MM. Milne-Edwards and Haime. But 

 other examples of rather more advanced growth have a less regular 

 form, and a greater number of lateral calices, while the earlier-formed 

 ones, near to the terminal calice, have increased visibly in size, and 

 do not differ much in this respect from it. I would suggest the 

 probability of the Genahacia Sancti-mihieli being merely the early 

 period of growth of some dendroid species of Thamnastrcea. 



In addition to the foregoing there are several species which are 

 represented by such unsatisfactory specimens that they cannot be 



