EXPLANATION OF PLATE I. G. 



LOWER PALEOZOIC CRUSTACEA. 



I ZETHUS ATRACTOPYGE (M<^Coy). Part of head and part of thorax, natural size, from the 



schists of Ravenstone Dale. 

 2 — 3 Pygidium, natural size, from the slate of Coniston. 



4 Ditto, magnified two diameters, Alt yr Anker, Meifod. 



5 Part of head, a little larger than natural. 



5 a Portion of ditto magnified. 



6 ZETHUS SEXCOSTATUS (Salt. Sp.) Pygidium, natural size from the schists of Rhiwlas. 



7 Larger individual, same locality. 



8 ZETHUS RUGOSUS (Port. Sp.) Pygidium, magnified three diameters (specimen in Mr Marshall's 



collection, Coniston limestone). 



9 CERAURUS CLAVIFRONS (Dal. Sp.) Profile of part of cephalic shield, natural size, from schists 



S. W. of Cefn Grugos. 



9 a Front view of another specimen (spaces enclosed by posterior furrows too small in this figure), 



schists of Cader Dinmael. 



10 CERAURUS OCTOLOBATUS (M-'Coy). Pygidium, natural size; Rhiwlas. 

 10 a The same, magnified. 



I I Pygidium, natural size, Alt yr Anker (formerly engraved by Mr Salter under the new name Phacops 



obsoktus, but now very properly considered indeterminable by him, or to belong to some Calymene). 

 12 PHACOPS ALIFRONS (Salt.) Cephalic shield, natural size (angles not perfect in specimen), from 



the impure limestone of Capel Garmon. 

 13 — 14 Pygidium, natural size. Limestone of Pont y Glyn, Diffwys. 



15 ODONTOCHILE OBTUSICAUDATA (Salt. Sp.) Cephahc shield, natural size, calcareous flags 



of Coldwell. 



16 Pygidium, natural size, same locality. 



17_18 PHACOPS APICULATUS (Salt.) Cephalic shields, natural size, schists S. W. of PwUheU and 

 Glyn Ceiriog. 



19 Pygidium, natural size, schists of Rhiwargor. 



20 ODONTOCHILE TRUNCATO-CAUDATA (Port. Sp.) (type specimen of Phacops affinis Salt.) 



Pygidium, natural size ; Caradoc sandstone, the HoUies, Church Stretton. 



21 Small specimen. 



22 CHASMOPS ODINI (Eichwald Sp.) Cephalic shield, natural size (Mr Salter's figure on this plate 



erroneously represents the angles as rounded — they are produced into long flattened spines, partially 

 broken off in the specimen), schists of Llansaintfraid. 



23 Pygidium, natural size, same locality. 



24—25 HOMALONOTUS BISULCATUS (Salt.) Portions of cephahc shield, natural size; from S. W. 

 of Pwllheli. 



26 Pygidium and part of thorax (this specimen is not in the collection). 



27 — 28 Pygidia, natural size, Caradoc sandstone of Acton Scott and schists S. W. of PwUheli. 



29 Part of small cephalic shield. 



30 — 31 Pygidia, supposed varieties, Ravenstone Dale, Maes Meillion. 



32 Undetermined. Schist near Bryn Eithin. 



33 ILLiENUS ROSENBERG! (Eich.) Part of cephalic shield, natural size; from the calcareous 



schists of Coniston. 



34 Thorax, same locality. 



35 Pygidium, same locality. 



36 ILLiENUS DAVISI (Salt.) Perfect specimen, natural size, from Rhiwlas (the figured specimen 



belongs to the cabinet of Mr Davis). 



iVofe.— The figures on this plate were engraved some years ago by Mr Salter, which accounts for representations of some 



specimens not in the Cambridge Collection. 



