8(5 " V ON THE TOPOaiiAPHY AND UF.OT.OGY 



SO numerous as to he always in contact. This peculiarity gradual]}^ changes to the 

 eastward, so that the conglomerate is represented on the ]Srigua by a group of beds 

 in part pure hmestone, in part an impure limestone, containing occasional pebbles. 

 This last is the stratum from which fossils were obtained. 



One bed near Maniel is made up of little grains half as big as an ordinary pea, 

 almost uniform in size and with Uttle or no cementing sand. On the Nigua Kiver 

 the limestone acquires its greatest development. Here the metamorphic action has 

 been unusually well marked and the formation is represented mainly by limestones 

 and jaspers. The stratification also is unusually well preserved, so that a good 

 section is attainable. The lime-strata of the Ocoa are apparently all repeated on the 

 JSTigua, and the conglomerates are replaced by beds containing but few pebbles, the 

 matrix being either a pure, or more usually, an earthy limestone. This latter rock, 

 at two localities on the river, yields fossils, in a bad state of preservation for 

 extraction, although occasionally recognizable. The shell substance is completely 

 crystallized so that it is next to impossible to extract a thick shell in such a manner 

 as to expose its surface. Of hundreds of attempts to obtain a specimen of a very 

 common Trigonia I have only succeeded once or twice in obtaining a little piece of 

 the surface ; the fracture always taking place among the crystals of calc-spar into 

 which the shell has been cemented. The univalve shells invariably break across and, 

 in a word, the collector has to content himself with the few imperfect fragments 

 found weathered out. I^owhere else have fossil moUusca been discovered in this 

 formation in Santo Domingo, and only in one other instance have I found any other 

 fossil in it. Three or four miles west of San Jose de las Matas I was fortunate 

 enough to discover two fragments of the same limestone, being of a dark bluish-gray 

 color, on the surface of which can be detected, faintly marked, the stars of a coral. 

 Doubtless by means of polishing they can be brought out. These are of especial 

 value, being the only traces of corals yielded to us by the formation ; unless indeed 

 a stray pebble, found on the surface of the ground near Bani, also containing corals, 

 may belong to the same group. On the Peninsula of Samana the limestones are 

 highly metamoriDhosed, and here occurs a very curious mixture. In some cases the 

 limestone has a few scattered scales of mica imbedded in it ; in others the mica is so 

 abundant as to form layers, while not infrequently, especially in the eastern part, 

 mica slate, alternating with the limestone, is not an unusual feature. This is the 

 more remarkable since it occurs nowhere else on the island, and in only one other 

 locality is mica slate found and there in hardly noticeable quantities. 



With so few data it would seem hazardous to venture a determination of the 



