186 Mr. H. J. Carter on Melobesia unicellularis, 



nearly all become dried up, this was again repeated, also with no 

 further change, the granular protoplasmic disk &c. remaining 

 as when the acetic acid first released it from the calcareous 

 cell. 



I now turned to look at the remains of the other entire 

 coccoliths which were present ; and they w*ere all in the same 

 condition, with the exception of the granule (nucleus ?) in the 

 centre of the transparent area (nuclear utricle?), which was 

 single, double, quadruple, or still more divided in different 

 cells respectively. 



Thus, still more convinced that I had a unicellular Alga 

 under examination, and taking a portion of the little arbores- 

 cent fronds of Melohesia calcarea ("the chalk-il/e/oZ'e6•^a"), 

 which, in about ten fathoms, occurs here in accumulated beds 

 or banks of probably miles, certainly acres, in extent, I pul- 

 verized a portion for examination, and observed several frag- 

 ments whose cells, but for their polygonal arrangement, pre- 

 sented very much the appearance of the coccolith in their 

 concentric lines, transparent area, and central granule, toge- 

 ther with the absence of blue colour under the iodine test. 



Lastly, considering that the coccolith is so abundant in the 

 Laminarian zone here, and so voraciously fed upon by the 

 Echinodermata and Ascidia3, also that it is so nearly allied in 

 composition, structure, and habit to Melohesia calcarea., that it 

 chiefly forms the bed of the Atlantic Ocean, and that it is 

 found fossilized in the chalk, I cannot help inferring that it 

 is a vegetable organism which contributes chiefly to form the 

 calcareous deposits of the present day in many parts, and has 

 done so in the formation of calcareous ones of the past, at all 

 events that of the chalk. 



With these views, then, leaving the terms " coccoliths" &c. 

 for the fossilized forms, I would propose the following name 

 and description for those now in existence : — 



Melohesia unicellularis , railii. 



Cell calcareous, discoidal, obtusely elliptical, transparent, con- 

 vexo-concave ; consisting of two convexo-concave disks, one 

 a little larger than the other, the larger one flattened on its 

 convexity, and receiving the smaller one in its concavity ; 

 enclosing a granular protoplasmic disk with oval transpa- 

 rent area (nuclear utricle'?), and within this a single granule 

 (nucleus?) ; the granule subject to 1, 2, 4 or more division. 

 Mode of propagation unknown. Size 1-1 700th of an inch 

 long and about 1-1 2000th of an inch thick. 



Hah. Marine ; accumulating in beds. 



