Clauk. — The Cidaridae. 



PLATE 10. 



1-2. Tretocidaris bracteata (A. Agassiz). Nat. size. 



1. Abactinal view of partly cleaned specimen. 



2. Side view of same. 



3-4. Goniocidaris umbraculum Hutton. Nat. size. 



3. Ambulacral view of bare test. 



4. Abactinal view of same. 



6. Goniocidaris tubaria (Lamarck). Nat. size. 

 Interambulacral view of partly cleaned, small 

 specimen, with slender spines. 



