258 THE AMERICAN MONTHLY [November 



Pterocanium^ 

 Ptcrocodon^ 

 Rhopalocan in m , 

 Sp o ngosp hcera^ 

 Stephanastnun^ 

 Stylocyclia^ 

 Stylodictya^ 

 Stylosp hcera^ 

 Thyrsocyrtis , 



Total, Barbadoes, 27S Sp'gf'd, 174 



That is to say, of the 27S forms found by Ehrenberg in the Bar- 

 badoes earth only 174 were found in material from Spingfield, 

 and 6 genera were not found there, namely, Calocyclas^ Carpo- 

 canium, Cryptoprora {^^ Scthatnpora') Dictyopodiu7n^ Pteroco- 

 don, Rnd Stephanastrnm. But from another district the mate- 

 rial yielded 72 additional species, including representatives of 

 all the 6 genera not found at Springfield. I call especial attention 

 to this, because the mere fact that one has some earth from 

 Barbadoes is no assurance that he will find all the forms men- 

 tioned above, or even all the genera. Some of the material was 

 very poor in both genera and species. Thus, that from Bissex 

 Hill yielded him only 5 genera and 7 species, though there are un- 

 doubtedly more in that material. 



Note, further, that besides these two divisions of the Radiolaria 

 there are two others, the spinous skeleton of which are seldom 

 observed, except in the living state. 



However, the student will find that these fossil forms will keep 

 him busy for a long time, while the illustrations of the Acantho 

 ffietrina and others, the skeletons of which are so loose that they 

 readily fall apart and are lost, can be seen in Haeckel's work, a 

 copy of which is fortunately at the command of every one living 

 near the Astor Library, New York (vol. iS of the Challenger Re- 

 port). If one is enthusiastic and rich (which unfortunately is 

 not often the case) he can procure a copy for himself, through 

 MacMillan, of New York, at the cost of some forty dollars, by 

 no means exorbitant, when you consider that it represents ten 

 years of laborious work, but still beyond the reach of most stu- 

 dents. 



A word or two more about the preparation and mounting of these 

 forms. I have given the simplest method, but if the student 

 becomes interested he will not be satisfied with that. The forms 

 will not be clean enough to suit him. After trying various meth- 

 ods, at the suggestion of a correspondent I tried that used by 

 Terry in cleaning diatoms, and described in a former number of 

 the Journal, only instead of mixing bi-chromate of potash with 

 the material and then adding sulphuric acid, I use chromic acid, 



