CHARACTERISTIC DEEP-SEA TYPES. SEA-URCHINS. 99 



The genus Rliynchopygiis appeared at the time of the chalk, 

 and is an interesting- West Indian type. It is found on both 

 sides of the Isthmus of Panama, and is characteristic of a period 

 when there was a direct connection between the Caribbean Sea 

 and the Bay of Panama. 



The aUied Neohimpas has no fossil representative. The aUies 

 of Conolampas date back to the cretaceous period, Conolamjms 

 Slgsbei (Fig. 3G8) is by far the most striking sea-urchin I have 

 seen. I shall always remember the particular haul, on the edge 

 of the Yucatan Bank, when the dredge came up containing half 



Fig. .368. — Conolampas Sigsbei. 1 



!• 



a dozen of these huge brilliant lemon-colored echini. This mag- 

 nificent species was originally referred to the fossil genus Cono- 

 clypus ; but Zittel having discovered that some species of this 

 genus possessed teeth, De Loriol made an examination of the 

 genus, and found that it really contained two generic types, one 

 edentate, the other provided with teeth. These discoveries led 

 me to make a renewed examination of Conocli/jms Sigsbei. 

 On opening a specimen I found that it was edentate. This 

 structural feature is most interesting, as it seems to show us the 

 direct passage, as it were, between the edentate echini and those 

 provided with teeth. 



Another typical genus from the chalk represented among the 



