14 MICROSCOPICAL EXAMINATION 



INFUSORIA. 



1 shall not enter into a detailed description of the Infusoria found in these 

 soundings, as the species detected were mostly such as are well known, and 

 which have a wide geographical range. In the deep soundings they consisted 

 chiefly of species of the genera Coscinodiscus, Actinocyclus, and Actinoptychus, 

 for figures of which reference may be made to figs. 10 to 15 of the second plate 

 of my memoir on American Bacillaria. 



Some of the other intei'esting forms are represented in the plate accompany- 

 ing this memoir. The following brief account of them, it is believed, will be 

 sufficient : 



Fig. 50. This appears to be the Dictyopyxis cruciala of Ehrenberg. It re- 

 sembles two thimbles joined together, with the whole surface covered with min- 

 ute cells, or projections so arranged as to give the appearance of two sets of 

 lines crossing each other obliquely. 



It occurs in No. 37, 19 fathoms, and is also a common fossil in Virginia. 



Fig. 51. This is a species o? Pinnularia^ probably new. 



Fig. 52. JVavicula sigma, Ehr. .'' 



Fig. 53. Periptera sp. .-^ Found in No. 37, 19 fathoms. Closely allied forms 

 are common among the fossil Infusoria of Virginia. 



Fig. 54. Triceratium favus, Ehr. An elegant cosmopolite species, easily 

 recognised by its large triangular form and hexagonal cells. I have found it 

 along our coast from Rockaway, Long Island, to Charleston, South Carolina. 



It also occurs in the mud of the Hudson river at West Point, and has also 

 been found in Europe and Asia. It has not yet been detected in the fossil state. 



Fig. 55. Triceratium allernans^ Bailey. I attach this provisional name to 

 the species represented in figs. 55 and 56. It is much smaller than the preced- 

 ing species and chiefly characterized by the three curved lines seen on its trian- 

 gular face, as I'epresented in fig. 56. It occurs in both shallow and deep sound- 

 ings, and also as a fossil. 



Fig 57. An interesting and probably novel form referable, I think, to Ehren- 

 berg's genus Denticella. The figure shows its form with suflicient accuracy, 

 but in consequence of its surface being obscured, I could not well make out the 

 character of the minute markings of the shell. For the present I shall call it 

 Denlicella dubia. 



It was found in H, No. 2, 10 fathoms, S. E. of Cape Henlopen. 



Fig. 58. Spicules of sponges, common in all soundings. 



Fig. 59. Frustule of Qrammatophora oceanica? common in shallow soundings. 



Fig 60. Dictyocha speculum, Ehr. Common in shallow soundings ; occurs 

 occasionally in deep soundings, and is also a common fossil species. 



Fig. 61 to 65. Different species (.'') of TLhrenherg's genus Rhaphoneis. These 

 were all found in the sounding H, No. 2, 10 fathoms, and are chieffy of interest 

 from their resemblance to species occurring abundantly in the fossil state in the 

 Meiocene infusorial strata of Maryland and Virginia. 



