122 PROCEEDINGS OE THE GEOLOGICAL SOCIETY. 



Actinozoa. — Rali/sites catenulatus, Linn., Favositesfihrosus, Goldf., 

 and Monticulipora favulosa, PhilL, complete the list of the Llandeilo 

 Actinozoa. No English form is known. North Wales yields Favo- 

 sitesfihrosus. All three occur in South "Wales, and Favositesfihrosus 

 in Ireland. Scotland has no representative. All three species pass 

 to the Caradoc. These are the first corals occurring in the British 

 rocks ; but they expand to 20 genera and 42 species in the succeeding 

 Caradoc. We cannot admit that change of condition only thus 

 favoured the growth and development of the Actinozoa. It is true 

 little limestone occurs in the Llandeilo, and that little in the upper 

 division ; but the organic remains in the Upper Llandeilo limestones 

 are chiefly Crustacea. The increase of limestones and calcareous 

 matter in the Caradoc rocks being due to life agency, we may 

 attribute much of it to the secretion of carbonate of lime by the 

 Ccelenterata. The only notable or appreciable form is Holy 'sites, 

 which was abundant. 



Echinodermata. — We know of only 4 genera and 4 species of 

 this class, which, like the Actinozoa, may be said to first appear in 

 the Llandeilo. None are known in the Arenig below ; but 4 species 

 (1 Menevian and 3 Tremadoc) in fragments have been preserved in 

 older formations. The 4 Llandeilo species are Actinocrinus Wynnei, 

 Echinosphazrites granidatus, Palaiasterina Kinahani, and Glypto- 

 crinus hasalis. The first 3 are Irish ; Glyptocrinus occurs in the 

 South-Wales Llandeilos. Two of them passed to the Caradoc. As 

 with the Actinozoa, this group became greatly developed in the 

 Caradoc, no less than 15 genera and 32 species enriching that for- 

 mation. These, like the corals, must have lived in a moderately 

 deep sea well charged with calcareous matter. 



Annelida. — It is questionable if more than 6 species (although 

 9 are placed in the Llandeilo) occur : Palceochorda teres, P. major, 

 and P. minor may be Arenig ; they are very sparingly distributed, 

 only 1 species occurring in England, South Wales, and North Wales, 

 and 2 in Scotland. I know of no Irish Llandeilo Annelida. 



Crustacea. — In this class the Trilobita are of high significance, 

 in both the Llandeilo and Caradoc formations, especially the latter, 

 in which we know of more than 100 British species. The Llandeilo 

 rockahave yielded 18 or 20 genera and only 45 species, or upon 

 the average only about 2 species to each genus. Many genera are 

 represented only by 1 species ; these are Homalonotus (H. hisul- 

 catus, Salt.), Lichas (L. patriarchus, W.-Edg.), Stygina (8. Murchi- 

 sonias, Murch.), Cheirurus (0. Sedgwickii, M'Coy), and Acidaspis (A. 

 Jamesii, Salt.). Much has yet to be done by collectors to increase 

 our knowledge of the specific crustacean fauna of the Llandeilo rocks. 

 South Wales being the classical locality for the Llandeilo group, it is 

 natural that we should expect to find there the largest and most 

 typical fauna, crustacean or otherwise. In one group (Graptolites) 

 we have seen that this is not the case, Scotland being most repre- 

 sentative. Here, however, the Crustacea of South Wales (29 

 species) are double those of North Wales (15), and ten times more 

 than those of Scotland, which has yielded only 3 species, conditions 



