212 



known to me of this genus, it being more than half "an inch 

 long, with a width of from two to three lines. The general 

 form, when the animal is creeping, is oblong or oval. Body 

 flattened, as usual. Anterior region obtusely triangular, much 

 less acute than in D. gonoceplidloides ; posterior region like- 

 wise less acuminated than in the latter. The transparent ce- 

 phalic spaces nearly circular. Color above generally of a deep 

 and uniform black ; sometimes, however, brownish black, but 

 never maculated. Under surface of body always lighter, 

 although of the same general hue as the upper one. Found in 

 great abundance in November last in the small rivulets emptying 

 into Tiber Creek. A few specimens were also obtained at Four 

 Miles Run, between Alexandria and Washington. 



This species is dedicated to Dr. E. Foreman, formerly of 

 Baltimore and now a resident of the city of Washington. I 

 am happy to have the opportunity thus afforded me of associating 

 his name with a department of Natural History in which he is 

 well known for his indefatigable zeal in collecting, and his dis- 

 interestedness in meeting the wishes of his friends. 



The discovery of a living species of the genus Amphidetus on 

 the American shores of the Atlantic must be regarded as an 

 interesting fact in the history of our radiated fauna. This dis- 

 covery might have been expected from the circumstance of the 

 existence of a representative of that genus during the myo- 

 cene period of the tertiary epoch in the southern part of our 

 country. 



The living species occurs under the same latitude, having 

 been found by Lieut. J. D. Kiirtz, at Folly Island, S. C. and by 

 myself at Cape Fear, N. C. 



Four recent species of Amphidetus are already known, three 

 of which are common to the basin of the Mediterranean, the 

 British Channel, and the North Sea, on the Coasts of England 

 and Sweden ; and a fourth, which has hitherto been found only 

 in the ^gean Sea. 



Four fossil species are likewise enumerated as having been 

 found in the tertiary strata ; one in Italy, two in France, and 

 another just alluded to, in South Carolina. Perhaps a fifth 

 species, from Maestricht, might prove distinct after a thorough 

 comparison of its structure with that of the other species. 



