81 



this single species. Fossil species with similar characters 

 are found in the cretaceous formations. This is the second, 

 Prof. A. remarked, of the '' old-fashioned " fishes, so to 

 speak, corresponding in their structure to fossil species, 

 which has been observed in this country. The other, the 

 Lepisosteus, is the only living representative of a large fam- 

 ily of fossil species. The existence of these two species has 

 undoubtedly reference to the fact, that America is the oldest 

 extensive continent which has been upheaved above the level 

 of the sea. In New Holland, two genera exist, bearing 

 similar relations to older families ; a fish, the Cestracion, 

 or Port Jackson Shark, and a shell, the Trigonia, which 

 have their analogues among the oolitic deposits. Prof. A. ex- 

 hibited a colored drawing of the new fish of which he was 

 speaking, by Mr. J. E. Cabot ; and presented specimens for 

 the cabinet of the Society. He has given it the name 

 " Percopsis,^^ on account of its resemblance to the Percoids. 



The second species, to which Prof. A. gives the name 

 Rhinichthys, is characterized by its long snout, the position 

 of the mouth beneath it, and the arrangement of the teeth. 

 The male is brighter than the female. 



This genus belongs to the family of Cypiinidce, and 

 should be placed in the vicinity of Barbus, though it has no 

 barbels. Leuciscus nasuius of Ayres, and L. atronasus of 

 Mitchill, belong to this genus. 



Prof. Agassiz also exhibited a colored drawing of Sphar- 

 gis coriacea, Leather Tortoise, which was recently cast on 

 shore at South Wellfleet, Cape Cod. It is the second only 

 of this species which has been obtained from our waters. 



Dr. Cabot stated that during a recent visit to the east end 

 of Long Island, he had made some interesting observations 

 on the formation of fresh water ponds by the closing up of 

 the entrances to inlets from the sea. About three miles 

 from the end of Montauk Point is such a pond, from four 

 to six miles in circumference, separated from the sea by a 

 sand beach about twenty rods wide. Within the memory 



PROCEEDINGS B. S. N. H. 6 MARCH, 1849. 



