290 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



DESCRIPTION OF PLATE 42 



PACK 



Matthevia variabilis Walcott 265 



Figs, i, la-b. (X 2.5.) End, summit, and side views of one of the most 

 characteristic forms of the species. 



2. (X 2.) A more conical form than the specimen represented by 



fig. lb. 



3. (X3-) Associated operculum with portions of the shell broken 



away. 



4. (X3-) Natural cast of the interior of an operculum. 



5. 5a-b. (X 3-) Side, end, and summit views of a conical specimen, 



having a deeply sinuous margin. 



6. (Natural size.) Cast of the interior of the chamber of habita- 



tion and inner chambers. The septa are seen at s, s'. The 

 outline of the shell about the chambers is traced. 



7. (Natural size.) Cast of the chambers of a more conical speci- 



men than that represented by fig. 6. 



8. (Natural size.) Cast of the chambers of a shorter specimen 



than those represented by figs. 6 and 7. 



9. (X6.) Natural transverse section of a specimen on a line 



of the septa separating the chamber of habitation and the 

 inner chambers. 



10. (X6-) Transverse septum separating one of the inner cham- 



bers and the chamber of habitation. 



11. (X5-/ Enlarged transverse section of a portion of a shell, 



illustrating the peculiar vesiculose structure of the shell. 



12. Enlargement of the interior surface of a part of a chamber of 



habitation, as seen on the specimen represented by fig. 7. 

 13- (X4-) Thin section of a portion of a shell, showing the 



vesiculose structure of the shell. 

 14. Diagrammatic vertical section to illustrate a shell (a, a) ; inner 

 chambers (c, c) ; chamber of habitation (d), and septa 

 (s, s) between the chamber of habitation and the inner 

 chambers. 



On the left side the transverse section of a shell (a), 

 and the inner chambers (c, c). 

 15- (X3-) End view of a conical specimen, showing the cast of 

 one of the inner chambers, the thickness of the outer shell, 

 and the papillose character of the outer surface. 

 All the specimens illustrated on this plate are included under one 

 number, U. S. National Museum, Catalogue No. 24598. From locality 

 (76), Upper Cambrian, Hoyt limestone, Hoyts quarry, 4 miles 

 (6.4 km.) west of Saratoga Springs, Saratoga County, New York. 



