116 



Family Astr^id^ — Group Astr^eaceje. 



A very interesting, but very imperfect fossil form of Plesiastrcea, is 



amongst the collection. The genus belongs to the Astrceacece or corals 



which have a massive structure, the individuals being intimately united, 



but multiplying by budding. The main distinguishing feature of 



Plesiastrcea is the possession of conspicuous pali, which, indeed, separates 



the genus clearly from every other species in the group. There are at 



most only eight species known, two of which are Australian, and one 



fossil. Three belong to the Pacific. In the species under consideration 



I am unable to speak very positively as to its character as the fragment 



is small and very much worn, in fact there is not a single perfect calice 



in the specimen. It has a very strong resemblance to Plesiastrcea 



Urvilhi in this that the calices are of equal size, and often oblong, in 



which respects it differs from P. Peronii, the form common on our 



coasts. Owing to the very complete details given by Messrs. Edwards 



and Haime in their diagnosis of the internal structure of P. Urvillei, 



which is living at King George's Sound, I am able to say that the fossil 



is new. 



Plesiastrcea St. Vincenti, n. sp. 



Corallum flat. Calices very slightly salient, very close, but with 

 distinct borders, circular or compressed. Costcs, continuous with the 

 septa, and projecting so as to unite at times with the contiguous ones of 

 the next calice, prominent above the margin. Systems, six ; Cycles, 

 four ; but the forth absent from some systems ; primaries, secondaries, 

 and tertiaries nearly equal, and extending to the pali, which are so worn 

 that it would be hazardous to attempt details, except that they seem 

 large. The edges of the septa seem to be dentate, much in the way that 

 is figured in the " Annals des Sciences Nat.," (vol. x., plate 9, fig 2a), 

 and the columella appears to be a few papillae. In a vertical section the 

 exothecal traverses are seen to be abundant, horizontal, and at irregular 

 distances, but there are about 20 in 10 millimetres. The endothecal 

 traverses are extremely irregular, thinner, sloping upwards at every 

 angle, and giving rise to a cellular tissue. In both these particulars it 

 differs remarkably from P. Urvillei. Diameter of calices, 3 rarely 4 

 millim. 



Is ote. — This coral which was first brought to my notice by my pupil, 

 Mr. Stirling Smeaton, occurs in large hemispherical, or flattish rounded 

 masses ; an imperfect lump measures seven inches in diameter, and from 

 two to three inches in thickness. Locality — Hallett's Cove, -St. Vin- 

 cent's Gulf (jR, Tate). 



