30 THE VOYAGE OF H.M.S. CHALLENGER. 



afl&nities in all possible directions, with the highly petaloid ambulacra of the Spatangoids, 

 with the simplest ambulacral petals of the earliest Spatangoids, or with the embryonic 

 ambulacra of the Pourtalesiae proper. 



Comparison between the Tertiary and Recent Echinids. 



In comparing the Tertiary fossd Echinids of the European beds with the species now 

 living in the West Indies, we cannot fad to be struck with the similarity existing between 

 them. It is well nigh impossible to distinguish the species, and even Cotteau hesitates to 

 consider them as specifically distinct. Compare thus the species of- Cidaris, Clypeaster, 

 Echinolampas, Schizaster, and Brissopsis, which are found in the Tertiary beds of Malta, 

 and are no longer found in the Mediterranean, having undoubtedly disappeared from there 

 as soon as the Mediterranean became a closed sea, and the temperature of the water became 

 raised above that of the ocean ;^ while, on the contrary, where the oceanic conditions have 

 not undergone any such great change, we find a remarkable identity in the genera of the 

 Tertiaries and of the surrounding deep sea, as can easily be seen by comparing the 

 Tertiary West Indies types '^ of Cidaris, of Echinolampas, of Agassizia, of Brissopsis, of 

 Schizaster, of Ettpatagus, oi Periptneustes (Meoma), oi Hemiaster, of Conoclypus, and of 

 Echinanthus, with the species of the same genera now found in the deep waters of the 

 Caribbean Sea and GuLf of Mexico. The presence of Clypeastroids in the Tertiaries of the 

 Mediterranean and Western France forms the connection which once must have existed 

 between the American Clypeastroids and those still found on the West Coast of Africa, 

 and extending from the Eed Sea to the Western edge of the Pacific realm. A trace of 

 this old connection is stiU shown at the present day in the existence of a species of 

 Mellita and of Moira in the Red Sea. 



Forbes, in his Monograph of the Echinodermata of the British Tertiaries, has figui-ed 

 under the name of Echinarachnius Woodii two species, one of which is probably a 

 Rhynchopygus or a very flat Niicleolites ; the other, a genus closely allied to one of our 

 deep-sea Pourtalesice ; it has the peculiar snout, thus far known only in that group. 

 Tlie relationship of the species of the older crag to the southern and eastern types was 

 already then insisted upon by Forbes ; while the newer crag manifests a more definite 

 connection with the present Fauna of Great Britain, and in the Pleiostocene of Norway 

 and North America we find the common StrongyJocentrot us drobachiensis, which is truly 

 an Arctic and boreal species, both in the Atlantic and Pacific Ocean. 



Laube^ describes from the Tertiary beds of Austrian-Hungary a species of Schizaster 



' A similar westward extension of the Tertiary corals of Sicily has been shown by M. Poiirtalfes, who also finds 

 Tertiary Sicilian corals still li\'ing in the deep waters of the Caribbean Sea. 



'^ See principally Cotteau, EchLnides d'Angmlla ; Guppy, West India Tertiaries. 



2 Dr Gustav C. Laube, Die Ecliinoiden der Oesterreichisch-Ungarischen oberen Tertiarablagerungen K. K. Geol. 

 Reichs Anstalt, Abhandl, v. Heft, No. 3, 1871. 



