PLATE XII a* 



GOMPHOCYSTITES TENAX, HaLL. 



Page 352. ' • 



Pig, 1. Lateral view of the upper part of the body, showing the arrangement of plates; the 

 spiral grooves indicating the places of the sessile arms are at the upper margins of the 

 ranges of smaller plates. The plates are more or less irregularly disposed in some 

 parts of the body, but they appear, like others of the genus, to have a generally 

 spiral arrangement. • (Enlarged to two diameters.) 

 ." 2. The summit, showing the arrangement of the spiral arms and the central aperture. The 

 diagram is made from an imperfect specimen, and the position of the eccentric 

 aperture could not be ascertained. 



GOMPHOCrSTITES CLAVUS, HaLL. 

 Page 353. 



Fia. 3. A fragment (natural size), showing the disposition of the spiral arms and the obtusely 

 angular form of the body below. 



GOMPHOCYSTITES GLANS, HALL. 

 Page 352. 



Fig. 4. Lateral view of a specimen, showing the entire form and the disposition of the spiral 

 arms. 

 " 5. The anterior ? view of another individual of the same species. 



HoLOCrSTITES ALTERNATUS, HALL. 

 Page 355. 



Fig. 6. A posterior ? view of a specimen (natural size), showing the position of the eccentric 

 aperture, form and relation of plates, etc. 



HOLOCYSTITES CYLTNDRICUS, HaLL. 

 ' Page 354. 



Fig. 7. View of a nearly entire individual, showing the central aperture in a depression at the 



summit. The plates of the lower part are broken off. 



" 8. A smaller individual, in which the plates have been strongly ridged, preserving a portion 



of the column. The lower ranges of plates are somewhat obscure, and the dotted 



lines indicate depressions, which may be sutures or only grooves in the larger plates. 



Apiocystites imago, Hall. 



Page 358. 



Fig. 9. Lateral view of the specimen, showing the ovarian aperture on the left-hand side of the 

 figure, and the right pectinated rhomb. (Figure natural size.) 



GrINOGYSTITES chrysalis, HALL. 

 Page 362. 



Fig-. 10. View of the gibbous side of the specimen. 

 " 11. Lateral view of the same specimen. 



*ThiB plate accompanied the origiual paper as Plate I. It is now arranged with the other plates in ils order 

 as XII a. 



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