i78 FAMILY GLOBIGERINIDA.. 



tow-net (?) at. the surface of the sea near Madeira ; and Prof Schultze thinks it the most pro- 

 bable supposition that the last chamber of the Ghhigerina, when it has attained a certain age 

 and size, separates hke the proglottis of a Tania, and, after living in a free state for a longer 

 or shorter period, effects the reproduction. Now I have very carefully laid open by the 

 application of dilute acid the spheres of a considerable number of Orhulines ; and I have not 

 met with a Ghhigerina in the interior of a single one. Without wishing to affirm that my 

 negative observation necessarily invalidates the statements just quoted (since it is quite 

 possible that, supposing OrhuIincB to be generative segments of Globigerina, the contents of 

 my specimens may not have been sufficiently advanced towards maturity at the time they 

 were gathered, to be recognisable in the dry state), it derives support from the following facts: 

 — 1. The marked difference in size between the OrbuJince and the Glohigerince of the same 

 " gathering," the diameter of the former averaging l-40th of an inch, and the smallest being 

 i-85th, whilst the diameter of the largest chamber in the latter averages 1-lOOth of an inch, 

 seldom exceeding 1 -80th. — 2. The perfect sphericity of Orhulina ; whilst the larger chambers 

 of ff/o^2j'm«a almost invariably depart considerably from the spherical form.^ — 3. The entire 

 absence of any indication whatever that Orhulina have been attached to, or continuous with, any 

 other organisms. — 4. The constancy of a large aperture in the segments of Globigcrina ,• whilst 

 it is deficient in so great a proportion of Orhulines that its presence may be considered as 

 exceptional. — 5. The absence in Ghhigerina of the larger pores by which the shell-wall of 

 Orhulina is so abundantly pierced. — Taken in mutual connection, therefore, the facts I have 

 adduced at present seem to me sufficient to justify the retention of Orhulina as a substantive 

 genus ; the only fact that occurs to me in support of its asserted relationship to Ghhigerina 

 being the generality of their association. Even this, however, does not appear to be uni- 

 versal ; for although at the present epoch the two forms generally occur together, this associa- 

 tion is by no means constant ; and, moreover, Ghhigerina presents itself much earlier in 

 Geological time than Orhulina. 



282. Affinities.— \i we consider Orhulina to be entitled to rank as a substantive genus, 

 we cannot hesitate in regarding it as the simplest conceivable form of the hyaline Forami- 

 nifera ; since it corresponds with that globular primordial segment, in which, as a rule, even 

 the most complex among them has its origin. In this way it may be said to be related to all 

 the higher forms ; but its nearest affinities are of course, on the one hand, to the mono- 

 thalamous types Ovidites, Lagena, and Spirillina ; and, on the other, to Ghhigerina, as being 

 that one of the polythalamous forms which most resembles an aggregation of monothalams. 



283. Geographical and Geological Distribution. — This genus, as Prof. Williamson remarks, 

 is a true cosmopolite ; being an inhabitant of all seas through a great range of depths. It 

 seldom presents itself, however, in shore-sands ; as it does not frequent shallow waters. On 

 bottoms of fine sand or mud, at depths of from 30 to 2350 fathoms, OrhulincB have been 

 found in abundance in every maritime region. Such a range in space, according to general 

 experience, would indicate a corresponding range in time ; but the rule does not seem to 

 hold good in this instance, for Orhulina have not been detected in any formation earlier 

 than the Miocene Tertiaries. It is especially abundant in the Vienna and Sub-Apennine 

 deposits. 



