293 HENRY B. BRADY. 



subject of careful investigatioiij the largest pelagic specimens 

 of each species having been measured side by side with good 

 average examples from bottom-dredgings. The result has 

 been to demonstrate that, with the possible exception of the 

 Orhul'incB, concerning which I shall have to speak presently, 

 the largest of those collected at the surface are smaller than 

 average adult bottom specimens. In all the species this 

 difference in size is apparent, though in some more than 

 others, but if drawings are made to the same scale the rule 

 becomes strikingly manifest. It would be easy to give 

 measurements in support of this point, but it seems better 

 to wait until the matter can be fully discussed Avith the aid 

 of plates. 



The thickness of the tests of some pelagic specimens has 

 been the ground of remark, and viewed by themselves the 

 largest examples of certain species are very stoutly built, but 

 as a matter of actual measurement they will not bear com- 

 parison with those found at the bottom. Thus, the stoutest 

 specimen of Sphceroidina dehiscens which I have been able to 

 find amongst the surface gatherings has a test of about 34)o 

 of an inch (0"05 millim.) in thickness, and the heaviest- 

 shelled Glohigeri7ia conglohata so collected is not more than 

 ■g-^-o of an inch (0"032 millim.), whilst bottom specimens of 

 either species, having shells -j^-^ of an inch (0"085 millim.) in 

 thickness, are not unusual. 



The case of Orhulina is somewhat different. The shells of 

 surface specimens are nearly as large as those of average size 

 from the bottom, but, whether spinous or not, they are 

 invariably very thin and delicate. Bottom specimens are 

 not only thicker, but vary very much amongst themselves in 

 shell texture and other particulars. The most noteworthy 

 structural condition found amongst the bottom specimens is 

 one in which the shell consists of a number of distinct 

 superimposed layers — sometimes four or five separate shelly 

 envelopes — one enclosed within the other, yet without any 

 absolute adhesion of their walls. In such cases the inner- 

 most layer is usually very thin and perforated with large 

 foramina, the outer ones coarser and thicker. Nothing 

 resembling the thick-shelled Orhdince, still less those with 

 multiple tests, has, so far as I know, been noticed amongst 

 the surface organisms. 



There is another fact connected with the subject which 

 has a certain amount of weight, namely, that though the 

 towing-net has been largely used in the British seas and in 

 areas at which GlohigerincB are found to a greater or less 

 extent at the bottom, no single specimen has been met with 



