412 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



DESCRIPTION OF PLATE 45 



PACE 



llhnnirus quadratus Hall ., 406 



Figs. I, ifl. (X i-S-) Dorsal and side views of the cast of a dorsal 

 shield preserved in fine-grained sandstone. U. S. National 

 Museum, Catalogue No. 62614. (Locality 78.) 

 lb. (Natural size.) Dorsal shield flattened in very fine-grained 

 arenaceous shale. U. S. National Museum, Catalogue No. 

 62615. 

 From locality 85, Upper Cambrian: Prairie du Sac, Wisconsin. 

 If, If'. (X I-5-) Dorsal and side views of a well-preserved ceph- 

 alon from the same layer of sandstone as the specimen 

 represented by fig. i. U. S. National Museum, Catalogue 

 No. 62616. (Locality 78.) 

 id, id'. (X I-S-) Dorsal and side views of a cranidium, showing 

 the form of the palpebral lobes and the course of the facial 

 sutures. U. S. National Museum, Catalogue No. 62617. 

 From locality 78b, Upper Cambrian : Saint Lawrence formation ; 

 Saint Croix River, near Osceola, Wisconsin. 



i^. (X I-5-) A pygidium associated with the specimens repre- 

 sented by figs. I and ir. U. S. National Museum, Catalogue 

 No. 62618. 

 The specimens represented by figs, i, if, and if are from locality 

 78, Upper Cambrian : Saint Lawrence formation ; Saint Croix 

 River, Osceola, Wisconsin. 



Mesoiiacis vermontana (Hall) A^7 



Fig. 2. (Natural size.) An entire dorsal shield from the type locality 



(25) at Georgia, Vermont, showing 14 thoracic segments 



of the Olenellus type, the spine-bearing segment, and ten 



segments of the Mesoiiacis type. U. S. National Museum, 



Catalogue No. I5399«- 



From locality 25, Lower Cambrian : Siliceous or finely arenaceous 



shale just above Parker's quarry, Georgia township, Franklin County, 



Vermont. 



The specimen represented by fig. 2 has been figured by Walcott, 

 Smithsonian Misc. Coll., Vol. 53, No. 6, 1910, pi. 26, fig. i. 



Mesonacis gilbcrti ( Meek) 406 



Fig. 3. (About >4 natural size.) The illustration is taken from a 

 plaster cast of the specimen now in the Geological Museum 

 of Princeton University, Princeton, New Jersey, which was 

 from locality 3511, Lower Cambrian : Mount Whyte forma- 

 tion ; eastern slope of Mount Odaray, above McArthur Pass, 

 British Columbia, Canada. Plastotype. U. S. National 

 Museum, Catalogue No. 62619. 



