a new Genus and Species of Silurian Corals. 391 



The coenenchjmal tubules are very variable in shape and 

 size ; but thej are always much smaller than the true corallites, 

 and are mostly oblong, triangular, or trapezoidal in shape 

 (tig. C). They are wedged in amongst the corallites, 

 round which they are usually disposed in a single row ; but 

 the zone thus formed is rarely or never complete, each coral- 

 lite coming into contact at different points with one, two, three, 

 or even four contiguous ones. In some cases, also, there may 

 be a double row of coenenchymal tubes between the corallites. 

 In internal structure the tubes of the coenenchyma possess 

 none of the special characters which distinguish the true 

 corallites, longitudinal sections showing them to be simply 

 traversed by numerous close-set, complete tabulee (J, fig. 1)) , 

 generally slightly curved, with their convexities directed down- 

 wards. Transverse sections also show them to want the cen- 

 tral tube of the true corallites and to be irreo-ular in form. 

 Though we have retained the name of " coenenchymal tubes " 

 for these, we think it most probable that they are really of the 

 nature of rudimentary corallites, which contained in the living 

 state a series of small and specially modified zooids. 



There are no traces of septa or of radial internal processes of 

 any kind, either in the ordinary corallites or in the coenen- 

 chymal tubes of PrasojJora. 



Affinities. The only forms with which it is necessary to 

 compare Prasopora are (1) Chcetetes and Alonticulipora^ (2) 

 Fistulipora and Callopora, and (3) Heliolites and its allies. 



The general appearance of the corallum in Prasopora, as 

 before remarked, is very closely similar to that of massive 

 examples of Cluetetes, Fischer, and Monticuliporay D'Orb. 

 From the forms included under these names, however, our 

 genus is widely removed by the possession of a well-developed 

 series of coenenchymal tubules (very different in character from 

 the minute tubuli found in many species of the two former 

 groups), and by the internal structure of the corallites. No 

 species of Chcetetes or Monticulipora, so far as we know, 

 exhibits any thing to be compared with the external zone of 

 vesicular tabulae and the central tube of the corallites of 

 Prasopora. 



To Fistulipora^ M'Coy, and the closely allied or identical 

 Callopora, Hall, the present genus is related by the fact that 

 the corallites are surrounded by a greater or smaller number 

 of coenenchymal tubules. The two former, however, have the 

 tubes of the corallites simply intersected by numerous com- 

 plete tabulge (said to be absent in some species of Callopora) ; 

 and neither of them presents any approach to the peculiar 

 structure of the corallites of Prasopora, though it is in their 



