TRANSACTIONS OF THE SECTIONS. 121 



lire of foreign bodies. Shells, therefore, of the delicate .and comparatively fragile 

 growth of Aspergillum would be liable to extreme contortion. Aspergillum vagini- 

 ferum, inhabiting the shores of the Red Sea, sinks into the sand, as may be seen 

 by the particles of sand and shell debris tbat become agglutinated to the sheath, to 

 the depth of eight to twelve inches and more ; the sheath is comparatively straight 

 and symmetrical, and the protruding end becomes furbelowed. A season of rest 

 ensues, another effort is made to extend the sheath, but the calcifying functions 

 either have done their part, or are enfeebled. A little is added to the sheath, and 

 the end is again furbelowed ; and in some specimens the process has been as many 

 as eight times repeated. 



In adherent species, only one of which, A. Strangei, inhabiting the shores of 

 N.E. Australia, has been discovered, the disc is very much pressed in. Two speci- 

 mens only have been collected, one affixed to the inner cleft of a mussel hinge, and 

 one attached to stone. The peculiarity of this form of Aspergillum is that the 

 sheath is formed in a square, and being formed, not in sand, but free, is tortuous and 

 enveloped by a slight periostracum. 



Dr. Gray has stated his opinion in a recent memoir in the ' Proceedings of the 

 Zoological Society,' that the sheath of A. Strangei is an enlargement of the primi- 

 tive pair of valves, and that it differs in this respect from the rest of the Aspergilla. 

 I incline to dissent from this opinion. Whether by a stretch of induction it be 

 regarded as an enlargement of the primitive valves, or not, the relation between 

 them I hold to be the same in the sand-inhabiting species, as in the adherent species. 

 Dr. Gray also draws a distinction between species which have a wavy depression in 

 the sheath around the circumference of the valves, regarding the wavy depression 

 as a part of the valves, of which only the umbones are seen. My own view is that 

 at the time of the metamorphosis of the mollusk, the valves are not larger in any 

 species than are defined by the smaller outline. When it is considered that the 

 valves are discarded at this time, but not entirely, inasmuch as they are appropriated 

 as material for a nucleus from which to develope a sheath, it is only reasonable to 

 suppose that the new sheath matter would, in some species, obtain a wavy deposit 

 corresponding with the outline of the nucleus. 



Hemarks on the Geographical Distribution of recent Terrestrial Vertebrata. 

 By P. L. Sclatek, M.A., Ph.D., Scc.Z.S. 

 After enunciating the principles of the distribution of organic beings according to 

 certain laws, independent of the influences of climate and other external conditions, 

 and that of the " continuity " of generic areas, which might, as a general rule, be 

 extended to all natural groups, small and large, the author proceeded to point out 

 what appeared to be the most natural primary divisions of the earth's surface, as 

 deducible from a careful study of the distribution of the terrestrial vertebrates. 

 These were : — ■ 



1. The Palaarctic Region, embracing Europe, Asia north of the Himalayas, and a 

 strip of Africa north of the Atlas. 



2. The ^Ethiopian Region, embracing Africa inclusive of Madagascar, and Arabia. 



3. The Indian Region, including Southern continental Asia, Sumatra, Borneo, 

 Java, and other islands down to the Straits of Macassar. 



4. The Australian Region, including New Guinea and adjoining islands, Australia, 

 New Zealand, and Pacific Islands. 



5. The Nearctic Region, including America down to the Southern limits of the 

 Mexican Table-land. 



6. The Neotrojncal Region, including the rest of the New World and the West 

 India Islands. 



These Regions were well characterized by their striking zoological peculiarities, 

 as shown by the preponderance of certain types and the absence of others in each ; 

 and by the fact that many of the families, more of the genera, and nearly all the 

 species found in each were as a general rule distinct, of which numerous examples 

 were given. These greater divisions of the earth's surface or regions were subdi- 

 visible into lesser areas or provinces, characterized by being the abode of distinct 

 species, which in many cases represented one another in their different localities. 



An inquiry into the meaning of these laws of geographical distribution was then 



