154 



PKOCEEDLNGS OF THE GEOLOGICAL SOCIETY. 



Echinodeemata. — It is clearly shown that this group requires to 

 he more carefully collected and studied. We have 5 genera and 5 

 species, or only 1 representative species to each genus. None occur 

 in Shropshire or Scotland. Two species, representing 2 genera, 

 have been met with in Pembrokeshire. The species are Actino- 

 crinus jpulchert, Cyclocystoides Bavisii, Salt., Palceaster coronetla, 

 PeriecJiocrinus moniliferus , and Palaiecliinus Phillvpsice, Forbes — 

 the last being the first known representative of the Echinoidea in 

 time. The Perischoechinidae, to which family this genus belongs, 

 attained its maximum development during the Carboniferous 

 period, both in Britain and America. No fewer than 7 genera 

 have been recognized in America and 4 in Britain. In the test 

 of Palceecliinus the interambulacral plates abut against each other, 

 not being bevelled for overlapping articulation, as is the case with 

 Perischodoinvs, Oligop7iorus, Melonites, and other genera. The family 

 Archseocidaridre, of which the Carboniferous genus Archceocidaris is 

 the type, does not occur below the Carboniferous rocks in any known 

 area. The modern representative, " Calveria" (C. hystrice) of Prof. 

 W. Thomson, has been dredged in 445 fathoms water (2670 feet) in 

 lat, 59° 38' K, long. 7° 46' "W. Calveria differs from all known 

 recent Echinoidea through the structure of the plates of the test, 

 which overlap, instead of abutting against each other, as in all other 

 genera. Again, the plates composing the interambulacral areas over- 

 lap from the apical disk towards the mouth, and those of the ambu- 

 lacral area from the mouth towards the apical disk, or in the reverse 

 direction. This ancient type appears in the Chalk as Ecliinothuria 

 (E. floriformis); and now, through the dredgings of the ' Porcupine/ 

 we have proof of its continuity from the Cretaceous epoch. 



Annelida. — Three genera, with four species, two of which claim 

 attention here, viz. Tentaculites {ornatus, Sow.), and Cormdites (serpu- 

 laria, Schloth.). They have occurred in almost every locality since 

 their first appearance in the Caradoc and Bala beds. Tentacidites 

 ranges through the Caradoc everywhere except in Scotland ; it is 

 abundant in the Lower Llandovery of South Wales ; but its maxi- 

 mum of development takes place in the May-Hill Sandstones, where 

 it is a marked feature in the fauna. It is sparingly exhibited in the 

 Wenlock shales and sandstones, Cormdites having replaced it indi- 

 vidually in those beds. Tentaculites anglicus, T. ornatus, and 

 T. tenuis are also Ludlow species ; and the long-lived T. anglicus 

 either passes to the Middle Devonian slightly modified, or is replaced 

 by Schlotheim's species T. scalaris. 



The 3 genera and 4 species (Comulites serpudarius, Tentacidites 

 anglicus, T. ornatus, and Spirorbis Lewisii) pass to the Wenlock. 



The Cephalobranchiate or Tubicolar Annulosa (Annelida) play an 

 important part in the life and distribution of the class through 

 time. Their habits insure persistency, their structure security, and 

 their bathy metrical ranges are such as to lessen their chances of 

 modification through relative changes of land and sea. ISTo form of 

 the order Errantia, or Dorsibranchiate Annelida, has been detected 

 in the Llandovery rocks, although, doubtless, they existed, as many 



