ROTALIINAE 407 



one-half the dorsal side (fig. 23). The tube is fimbriated, or broken up by solid partitions 

 starting from the outer edge of the tube and separating it into finger-shaped or forked 

 pockets, which give a very ornamental appearance to the test. After about three convo- 

 lutions the test assumes the normal patelline mode of growth, and, except for size and 

 distinctness of markings does not differ from Williamson's Type. 



Diameter, up to 0-70 mm. 



It is not uncommon to find specimens of P. cornigata in which the early portion of the 

 test following the proloculum consists of an undivided tube, but it is rare to see more 

 than one or two convolutions of the spiral, and we have never before met with specimens 

 in which the spiral portion is fimbriated. The fimbriations are similar in nature to those 

 causing the markings which give its characteristic appearance to the dorsal view of 

 P. cornigata. 



Genus Patellinoides, gen.n. 



Test free and conical, more or less depressed, more or less oval in plan, commencing 

 with a proloculum, followed by a simple spiral chamber of 1-2 convolutions ; the growth 

 then becomes alternate, crescentiform chambers being arranged opposite to one 

 another as in Patellina cornigata, but remaining entire throughout the growth. There 

 are no internal septa dividing the chambers into chamberlets, but the outer margins of 

 the chambers on the dorsal side are sometimes marked by an irregularly scattered line 

 of minute dots, which look like perforations, but in balsam and under a high power 

 appear to be pillars of solid shell-substance, which may represent vestigial secondary 

 septa. The ventral side is slightly concave, filled with a glassy shell-substance, to one 

 side of the centre of which is a small arched aperture communicating with the final 

 chamber, apparently by a curved tube. The aperture is ahernately to the right and left 

 of the centre, and facing in opposite directions with the addition of each chamber. 



Several authors (e.g. B. 1884, FC, p. 633; C, 1928, F, p. 268) have referred to the 

 existence of specimens of Patellina without divisions to the chambers. It is not clear 

 whether they are referring to P. cornigata, Will., or to the very minute P. campanaeformis 

 (B. 1884, FC, p. 634, Text-fig. 19). At any rate we are not aware of any figures of 

 unseptate specimens other than P. campanaeformis, which is an organism of such extreme 

 rarity that it is unlikely to have come under frequent observation. Cushman, it is true, 

 in 1928, created a genus Patellinella in which the chambers alternate, two to a whorl, 

 and are free from secondary septa. But it is based on Textiilaria inconspicua, Brady, an 

 organism of somewhat doubtful affinities, but probably not closely related to Patellina. 



Unseptate Patellinae do however exist, though they are extremely rare by comparison 

 with the ubiquitous P. cornigata. For many years past we have met with an occasional 

 example in British gatherings, but have hitherto regarded them as abnormal individuals 

 of the type. The occurrence of two very distinct forms in the Falkland material, and in 

 sufficient numbers to indicate their character, has forced us to the conclusion that the form 

 must be recognized as generically distinct. There are no transition forms in the Falkland 

 material, in which Patellina cornigata is very generally distributed and very true to type. 



