6 R. Tate — Census of the Lias Incertebrata. 



Purpiirina, Pileolus, Pterocera, Pimula, Pundurella, Pyrula, Tedaria, 

 Tornaiella (?), and Turhinella begin with the Lias. No genus of 

 Gasteropodous shells is peculiar, if we except Pteroeheilos and 

 Pleurwtella (Moore), which appear to be founded on immature indi- 

 viduals, and, consequently, may prove eventually to belong to known 

 genera. 



Class Conchifbra. — Here, also, the majority of the genera com- 

 menced in the Trias, whilst a few range from Palaeozoic times 

 through succeeding formations, such as Cypricardia, Pinna, Solemya, 

 Inoceramus, etc. Axinopsis and Myophoria do not pass beyond the 

 Lower Lias. Protocardium, Cythere, Pholadomya, Gastroch(Bna Pla- 

 cunopsis, Saxicava, and Tancredia date from the Ehsetic ; whilst 

 Exogyra, Fistulana, Gresslya, Goniomya, Homomya, Liniopsis, Pleuro- 

 mya, Pholas, Pteroperna, Sowerlya, Spondtjlus, Thracia, Trigonia, 

 Teredo, JJnicardium, and Venus are not older than the Lias. The 

 following genera are peculiar, Cardinia, Conchodon, Sippopodium, and 

 Terquemia. 



Class Beachiopoda. — The majority of the genera have an ex- 

 tensive range; Leptcena becomes extinct in the Upper Lias. Megerlea, 

 Terehratella, TerelratuUna, and Zellania commence in this system, and 

 Suessia is confined to it. 



Class Polyzoa. — With the exception of Berenicea, all the genera 

 of Polyzoa date from the Lias. 



Class Crustacea. — All the Malacostracous Crustaceans belong to 

 Mesozoic genera; Scapheus is peculiar. Of the Entomostraca, all 

 have a wide range, if we except Aspidocaris, recalling the Palaeozoic 

 genus Discinocaris. which is Triassic and Liassic. Of the Cirripedia, 

 Poliicipes dates from the Ehsetic, and Zoocapsa is peculiar. 



Class Annelida. — Terelella and Vermicularia commence in the 

 Lias, the other genera are much older. 



Class Eghinodermata. — Excepting Cidaris and Rhaldocidaris, 

 which are also Triassic, all the genera of Echinidea date from the 

 Lias ; Microdiadema is peculiar. All the genera of Ophiuridea are 

 represented in existing seas ; so also the Asteriadea, excepting Tropi- 

 daster and Plumaster, which are peculiar. The Crinoidea comprises 

 Pentacrinus ranging from the Trias, Apiocrinus, Cotylederma, and 

 TJugeniocrinus from the Lias, and Extracrinus and Microcrinus, which 

 are peculiar. 



Class Zoantharia. — About one-half the genera of corals are re- 

 presented in the Trias, a few are peculiar, whilst the rest range 

 upwards from the Lias. 



Class Spongida. — Neurofungia is doubtfully peculiar. 



If we confine our attention to the succession of life in the British 

 strata, then the generic grouping in the three members of the Lias 

 becomes more pronounced : — the Middle Lias being the horizon at 

 which appear Rotella, Niso, Opis, and Limea; the Upper Lias the 

 same for Trigonia, Corhis, Cyihere, and Macrodon. 



The distribution of some of the peculiar and restricted genera in 



