6 MICROSCOPICAL EXAMINATION 



well preserved plates from the column of a species of encrinite. The gravel 

 also afforded two valves of Astarte castanea Say. By levigation it yielded a 

 very small number of silicious Infusoria. 



G, No. 27, 20 fathoms ; lat. 38° 41' 00"; long. 74° 06' 00". 



A fine grained sand with black specks. A few fragments of bivalve and uni- 

 valve shells, small spines, and numerous plates of an echinoderm, like those in 

 F, No. 27, and some Polythalamia, were detected in this specimen. Among the 

 Polythalamia were the Triloculina (T. brongniartiana.'' D'Orb.) represented 

 in figs. 44, 45. The large species of Robulina (R. D'Orbignii, fig. 9 and 10) 

 rather common, and several specimens of a minute species of Rotalina. 



By levigation a considerable number of Infusoria were obtained, among which 

 were Coscinodiscus lineatus, and undetermined fragments of other species. 

 Actinocyclus in fragments also. Actinoptychus senarius, Gallionella sulcata, 

 Stauroptera aspera, Striatella arcuata, a sigmoid Navicula, N. sigma Ehr., fig. 

 52, Dictyocha speculum, fig. 60, with some spicules of sponges. A few of the 

 minute globular bodies, fig. 49, (eggs of Polythalamia.'') were also seen. 



G, No. 31, 50 fathoms; lat. 39° 20' 38"; long. 72° 44' 35". 



This sounding is composed of a fine grained grayish sand with much mud. 

 It contains a considerable number of Polythalamia, among which were Margin- 

 ulina Bacheii, rather common ; Robulina D'Orbignii Bail., figs. 9, 10, Globigerina 

 rosea.'' D'Orb., common, but not so much so as in F, No. 25. 



The forms obtained by levigation were perfect discs of Coscinodiscus oculus- 

 iridis, Triceratium alternans, fig. 55, Gallionella sulcata, and some spiculae of 

 sponges, fig. 58. 



G, No. 8, 89 fathoms; lat. 39° 31' 00"; long. 72° 11' 20". 



Coarser than the last, not so muddy, and about the same color. It abounds 

 in Textularia atlantica^ fig. 38 to fig. 43, and in Globigerina, fig. 20 to 24; Mar- 

 ginulina Bacheii is also present; some specimens of Orbuhna universa, fig. 1, 

 and of Robulina D'Orbignii were also noticed. 



Only a very small number of Infusoria were detected by levigation. These 

 were, one specimen of Coscinodiscus patina, and a few frustules of Gallionella 

 sulcata. A few silicious spiculse, and some of the supposed ova of Polytha- 

 lamia, fig. 49, were noticed. 



FOURTH LINE OF SOUNDINGS. 



From line H, southeast from Cape Henlopen. 



H, No. 2, 10 fathoms ; lat. 38° 46' 40"; long. 75° 00' 30". 

 A fine sand, slightly muddy, containing a few small spines of an echinoderm, 

 one specimen of Triloculina, and a few minute nautiloid Polythalamia. 



