GENUS UVIGERINA. 109 



of the aggregation of segments to be quite subordinate in essential importance to those cha- 

 racters which appertain to each segment in detail; such as, in this instance, the strongly 

 marked peculiarity of the aperture, and the sui-face-ornamentation, by both of which tlie real 

 affinities of PuJymorph'ma are shown to be with the group of genera of which we have taken 

 Lagena as the type. 



263. Geoyrapldcal Distrilmtion — This genus shows itself under some or others of its 

 protean forms on nearly all the coasts wliich have been yet explored, alike in arctic, tempe- 

 rate, and equatorial seas. It does not often present itself in the deepest dredgings or sound- 

 ings, but is most common in sl)ore-sands and in dredgings from shallow waters. 



264. Geolof/ical Distrih/iHo/i. — The earliest appearance yet recognised of Polijinorplnna 

 is in the Upper Trias. It is common in the Chalk-marl, in which several of its varieties 

 have been met with ; in the Chalk itself it occurs more rarely. It is extremely plentiful in 

 many of the Tertiary deposits, as those of Grignon, Tours, Bordeaux, Vienna, and Palermo ; 

 and in the Post-tertiary clays of Lincolnshire. 



Genus V.— Uvigerina {Willimmon, Plate V, figs. 138—140). 



265. Histori/. — With the exception of Soldani, who figured certain fossil forms of this 

 genus (ci) under the name of Polijmorpliina plneifornm, no systematist appears to have 

 noticed it previously to the characterisation of the genus by D'Orbigny (lxix) in 1825. 

 The name which he gave to this type appropriately indicates the resemblance of some of its 

 forms to a bunch of grapes. 



2G6. External diameters and. Internal Structure. — The essential character of this type 

 consists in the triserial arrangement of its lagcniform chambers, which are disposed some- 

 what irregularly around an elongated axis, so as to form a spire having the proportions of 

 that of a Mitra. The aperture (ex, figs. 13S, 139) is a distinct round passage, with an 

 everted lip, generally set upon a tube more or less prolonged outwards, and sometimes 

 faintly toothed. When the tubular mouth is much elongated, and the chambers are globular 

 and distinct, the entire shell presents a well-marked racemose shape ; but in other forms 

 the surfaces of the segments arc flattened against each other and are also compressed 

 externally, so that the transverse section of the sliell becomes triangular. The triserial 

 arrangement, however, is not always maintained ; for in certain elongated forms of feeble 

 growth we find the later chambers loosely set on, and approaching a biserial or even a uniserial 

 arrangement ; such forms are figured by Soldani, and present themselves also in J'lngvrince at 

 present existing in the Mediterranean. There are even cases in which the triserial mode of 

 growth seems altogether wanting, and the biserial almost obsolete ; Mcs.srs. Parker and 

 Rupert Jones having specimens from shell-beds in the tropical and sul)-tropical parts of the 

 Indian Ocean which might be easily mistaken for Nodosari/ia, but whose Uvigerine character 

 is marked by the short, wide, strongly labiate aperture. It seems to have been a specimen 

 of the biserial type, that was figured by D'Orbigny (lxxiit) under the name of SayrUui 



