PLATE IV h. 
Legend, pa. Posterior adductor scars. in. Median muscular fulcrum, 
aa. Anterior adductor scars. v. Vascular sinuses, 
b. Brachial muscular scars. 
CRANIA, Retzius. 
Page 145. 
Crania Ljelia, Hall. 
Fig. 1. Four individuals attached to the pedicle-valve of Streptorhynchnk planumbonum. 
Hudson River group. Oxford, Ohio. 
Crania agaricina, sp. nov. 
Fig. 2. An individual attached to a branch of Thbmatopora ; showing the characteristic sparse and 
relatively coarse radiating ribs. X 3. 
Lower Helderberg group. Near Clarksville. N. Y. 
Crania pulchella, sp. nov. 
Fig. 3. An individual attached to the valve of Orthis subcarinata. It differs from the preceding species 
in its finer, more numerous ribs and greater size. X 2. 
Lower Helderberg group. Near Clarksville, N. Y. 
Crania Bordeni, Hall and Whitfield. 
Fig. 4. An individual attached to a valve of SpiHfer Oweni; showing the very fine radiating striae, and 
the conformation of the upper valve to the surface of attachment. 
Fig. 5. Profile of the same specimen. 
Hamilton limestone. Clarke county, Indiana 
Crania crenistriata, Hall. 
Fig. 6. The interior of an upper valve ; showing the strong anterior adductor scars and very faint poste¬ 
rior adductors. X 2. 
Hamilton limestone. Falls of the Ohio. 
Fig. 7. A portion of a cast of the internal surface in a decomposed chert; showing the filling of vertical 
canals. X 25. 
Corniferous limestone. Canandaigua, N. Y. 
Fig. 8. The interior of an upper valve ; showing the very strong anterior adductor scars with mar¬ 
gins elevated, and the more obscure posterior scars. X 3. 
Hamilton limestone. Falls of the Ohio. 
Fig. 9. The exterior of a large upper valve. Natural size. 
Hamilton group. Canandaigua Lake, N. Y. 
Fig. 10. A smaller uncompressed individual. 
Fig-. 11. Profile of the same. 
Hamilton group. Western Neio York. 
Fig. 12. A valve of the same, or a closely allied species, attached to Orthis impressa. X 5. 
Upper Devonian. Rockford, Iowa. 
Crania Rowleyi, Gurley. 
Fig - . 13. An individual showing the upper valve. X 2. 
Choteau limestone. Pike county, Missouri. 
Crania setigera, Hull. 
Fig. 14. An individual, referred to this species with some hesitation ; attached to a branch of Monticdli- 
pora. It will be observed that for some distance about the anterior edges of the shell, where 
the valves opened for the admission of food-bearing water-currents, the outward growth of 
the bryozoan cells has been obstructed. X 2. 
Trenton horizon Minneapolis, Minnesota. 
Fig. 15. An upper valve. X 2. 
Fig-. 16. Profile of the same. X 2. 
Trenton limestone. ' Mineral Point, Wisconsin. 
Crania spinigera, Hall. 
Fig. 17. The original specimen ; an individual attached to the shell of Rhynchonella Stricklandi. The 
ornamentation consists of radiating rows of sharply defined tubercles. X 3. 
Niagara group. Waldron, Indiana. 
