GEOLOGICAL SUCCESSION OF THE ECHINI. 751 



and they are replaced in a measure by the smaller Clypeastroids, Lenita, Scu- 

 tellina, and such Laganum-like genera. In the Miocene the large Clypeas- 

 troids, such as Echinanthus and Clypeaster, which first appeared in the 

 Eocene, take a marked development and form the principal species ; with 

 them come to light the Scutellidae proper, until in the Pliocene the character 

 of the genera is eminently recent, and we find such genera represented as 

 Mellita and Echinarachnius among the Clypeastroids ; the Arbaciadae, Sal- 

 macis, and Temnopleurus among the Desmosticha, while there are no genera 

 of Petalosticha which have not already occurred in the Miocene. It is quite 

 striking that when we compare the Cretaceous, Eocene, Miocene, and Plio- 

 cene genera with those of the present day we find a greater proportion of 

 them in common the farther west we go. Many of the genera of the Num- 

 mulitic period in India are still found in the West Indies which are entirely 

 extinct from the Pacific Ocean to the Mediterranean. 



The close relationship existing between the present fauna and the later 

 Tertiary period, the Pliocene, is best shown by a comparison of the repre- 

 sentatives of the present West Indian fauna with the fossils known to occur 

 in the Pliocene of the east coast of the United States and of the West Indies. 



PLIOCENE. WEST INDIES. 



Cidaris armigera, Mort.* Dorocidaris papillata. 



(Coelopleurus) Echinus inflatus, Moist. Coelopleurus floridanus. 



Echinometra acufera, Guppy. Eehinoinetra subangularis. 



Scutella Rogersii, Mort. ? 



Mellita caroliniana, Rav. Mellita testudinata. 



Mellita a'mpla, Holmes. Mellita sexforis. 



Clypeaster rosaeeus, Duch. Echinanthus rosaceus. 



Nucleolites Richardii, DncH. Rhynchopygus caribaearum. 



Pygorhynchus jamaicensis, Conk. Echinolampas depressa. 



Echinoneus cyclostomus, Guppy. Echinoneus semilunaris. 



Agassizia porifera, McCr. Agassizia excentrica. 



Brissus Scillae, Guppy. Brissus unicolor. 



Plagionotus Ravenellanius, McCr. Meoma ventricosa. 



Plagionotus Holmesii, McCr. Metalia peetoralis. 



Amphidetus gothicus, McCr. Echinocardium eordatum. 



Echinocardium orthonothum, Conr. Echinocardium flavescens. 



Schizaster atropos, D'Orb. Moira atropos. 



A similar comparison has already been made by Forbes in his Monog. of 

 the Brit. Tert. Echin. with those of the surrounding seas and the Mediter- 

 ranean, and many of the species he proved to be identical. Two of the 



* The authorities denote simply the specific determinations of the collectors. 



