NOTES ON llETICULARIAN RHIZOPODA. 285 



necessary to recognise and to give briefly the distinguishing 

 characters of each. 



Glohigerina huUoicles, d'Orbignv (' Annales des Sci. Nat.,' 

 1826, vol. vii, p. 277, Modeles No. 17 and 76).— D'Orbigny 

 described this species at four or five different times and 

 never in quite identical terms, but his Model No. 76 may 

 be accepted as a fair summary of the characters intended, 

 and this presents the general features of the variety most 

 abundant in the northern seas. The test is convex, the 

 segments spherical and few in number, that is, about four in 

 each convolution and seldom more than two convolutions, 

 and the inferior surface is excavated at the umbilicus, forming 

 a recess or vestibule into which the apertures of the indi- 

 vidual segments are directed. In this simplest form we have 

 a tangible and easily recognised starting-point. Though it 

 does not represent the best development of the type it is the 

 beginning of a chain, the successive links of which, some of 

 greater some of less morphological significance, have none 

 of them any pretension to rank as true species, but which 

 collectively extend over an area of variation so large that 

 the salient points must, of necessity, be distinguished by 

 trivial names. The following notes indicate the directions 

 in which these variations take place, the right precedence in 

 nomenclature being as far as possible observed. 



Glohigerina duhia, Egger (' Neues Jahrb. fiir Min.,' 1857, 

 p. 281, pi. 9, figs. 7 — 9) — represents the best development of the 

 ''hulloides^'' type. It has a fine, thick, regular shell with about 

 three convolutions, each consistingof five or sixsegments. The 

 segments.are relatively small, the peripheral margin rounded 

 and lobulate, and the umbilical vestibule deeply sunk. 



Glohigerina cretacea, d^Orbigny (' Mem. Soc. geoL, Fr.,' 

 vol iv, p. 34, pi. 3, figs. 12 — 14) — is, on the other hand, 

 a starved form, of small dimensions, thin and flat-topped, 

 the inferior surface concave. It also shows the umbilical 

 vestibule, and differs from Gl. huUoicles chiefly in its depressed 

 contour, and the more compact fitting of the segments, 

 especially the earlier ones. 



Glohigerina (Bquilateralis , nov. — This is a variety approach- 

 ing Hastigerina, in general form. The test is planospiral 

 and symmetrical, not Rotalian ; it consists of but little more 

 than a single convolution, and the whole of the segments are 

 sometimes visible on both sides. The final segment is often 

 smaller than the penultimate, as is sometimes also the case 

 with Gl. cretacea. 



