386 SMITHSONIAN .MISCELLANEOUS COLLECTIONS VOL. 53 



DESCRIPTION OF PLATE 26 



PAGE 



Mesonacis vennontana (Hall) (See pi. 44) 264 



Fig. I. An entire dorsal shield from the type locality (25) at Georgia, 

 Vermont, showing 14 thoracic segments of the Olencllus type, 

 the spine bearing segment, and ten segments of the Mesonacis 

 type. Natural size. U. S. National Museum, Catalogue No. 

 15399a- 



2. Posterior portion of the specimen represented in fig. I. 



The specimen represented by figs, i and 2 has been figured 

 by Walcott [1885, figs, i and 2, p. 329; 1886, pi. 24, figs, i, 

 \a-b ; and 1891a, pi. 87, figs, i, ia-h\. 



3. Pygidium, ten Mesonacis thoracic segments, the spine bearing, 



and two Olenellns-Vike segments, of a broad form of Mesonacis 

 vermontana 6 cm. in length. X 2. This is very much like the 

 posterior portion of fig. i. Same locality (25) as fig. i. U. S. 

 National Museum, Catalogue No. 15399&. 



Mesonacis ? mlckivitzi (Schmidt) 262 



Fig. 4. Portion of the thorax with seven segments in advance of the 

 spine bearing segment and five between the latter and the 

 pygidium. 



This figure is a copy of the figure given by Schmidt, 1888, 

 pi. I, fig. I, with the exception that the cephalon is not at- 

 tached as it was theoretically placed there by Schmidt. 



Mesonacis torelli (Moberg) 264 



Fig. 5. Drawn from a plaster cast of the cephalon figured by Moberg 

 [1899, pi. 15, fig. la]. Natural size. The cast is in the U. S. 

 National Museum, Catalogue No. 24631a. 

 5a. Side view of the specimen represented by fig. 5, showing base 

 of cephalic spine. 



Figure Sa is copied from Moberg, 1899, pi. 15, fig. ib. 



6. Central portions of a cephalon. Natural size. U. S. National 



Museum, Catalogue No. 56793a. 



7. Genal angle and spine. X i-5- 



Figure 7 is copied from Moberg, 1899, pi. 15, fig. 4. 



8. Drawn from a plaster cast of the pygidium figured by Moberg 



[1899, pi. IS, fig. 14]. X2. Cast in U. S. National Museum, 

 Catalogue No. 24631b. 



9. Hypostoma. X i-S- 



Figure 9 is copied from Moberg [1899, pi. 15, fig. 6]. The 

 specimen is redrawn in figs. 10 and loa of this plate. 



10 and loa. Top and side view of a plaster cast of the hypostoma 

 figured by Moberg and copied in fig. 9 of this plate. X i-5- 

 Cast in U. S. National Museum, Catalogue No. 24631c-. 



II. Thoracic spine. X i-5- [After Moberg, 1899, pi. 15, fig. i5-] 

 Cast in U. S. National Museum, Catalogue No. 24631^. 



