52 Notes and Comments. 



Fell Top Limestone of Northumberland and its equivalent 

 horizon in Teesdale, the Botany Beds. Since this form has 

 been confounded with another Carboniferous species, well 

 known under the name of ' Phillip sastrce a radiata (S. Wood- 

 ward),' it has been found advisable, in fact necessary, to 

 extend the original scope of the paper so as to include a revision 

 of the genus Phillip sastrce a and a description of ' Ph. radiata * 

 and its allies, which he has grouped together under a new 

 generic name, Orionastrcea. Several type-specimens, including 

 that of Phillipsastrcea hennahi (the genotype of Phillip sastrce a), 

 are described and figured. The new genus from the Fell 

 Top Limestone is a very distinctive form, on account of the 

 remarkable annular wall developed within the theca, and may 

 prove of considerable value as a zonal index. The corallum 

 in this genus, as also in Phillipsastrcea and in Orionastrcea r 

 represents a stage in colonial development in which the epitheca 

 of the individual corallites has entirely disappeared, and these 

 are consequently united by their dissepimental tissue — a 

 type of colony to which the term ' Astraeiform ' may be applied. 



DIAGNOSES. 



Aulina rotiformis. — The corallum is massive, and the 

 corallites are united by their extrathecal tissue ; all the septa 

 dilate at the theca, and those of the major cycle again dilate 

 at their axial edges, in such a manner as to fuse together, and 

 so build a cylindrical wall or tube within the theca. The 

 structure of the form is in most respects similar to that of 

 Phillipsastrcea, but it appears to carry forward the septal 

 characters peculiar to that genus to a further stage of devel- 

 opment. 



Phillipsastrcea. — The corallum is composite and massive ; 

 the corallites are united by their dissepiments, or are only 

 separated by a thin epitheca ; in the former case, the septa 

 are often confluent. Major and minor septa dilate at the 

 theca ; the latter terminate there, and the major septa atten- 

 uate and advance into the intrathecal region, and there often 

 dilate again at the axial edge. The central part of the corallite 

 is occupied solely by tabula?. 



Orionastrcea. — The characters of this genus are essentially 

 those of Lithostrotion, but of a modified form. The corallum 

 is composite and massive, and the corallites are either defined 

 by a thin epitheca, or, in the more typical instances, by no 

 epitheca at all ; in this latter case, the corallites are united by 

 their dissepiments and the septa are confluent. 



The distinguishing characters of the three species recognized 

 and described are as follows : — 



i. O. ensifer (Edwards & Haime). Septa not confluent. Culumella present. 



2. O. phillipsi (McCoy) Septa confluent. Culumella present. 



3. O. placenta (McCoy) Septa confluent. Culumella absent. 



■ Naturalist, 



