Nomenclature of the Foraminifera. 177 



D^Orbigny's Model No. 71 (Rotalia pidchella, D'Orb.) is one 

 of the nearest to this variety {R. sinuata), which is world-wide. 



27. Nautihxs Auricula. Page 108. Var. a. pi. 20. figs. a-c. 

 " Soldanij Tcstaceogr. vol. i. pi. 50. tig. Y." " Fossil : Coron- 

 cina." 



Var. /9. pi. 20. figs. d-f. " Recent : zoophytic concretions, 

 Mediterranean." 



These are delicate oblong varieties of Rotalia repanda, with 

 rapidly increasing chambers. They bear the same relation to 

 their type as Ximionina Scapha does to Nonionina asterizans and 

 Puh/stome//a crispa. 



The intermediate links between the typical R. repanda and 

 R. Auricula are found in the less oblong forms common in some 

 of the Subapennine Tertiary beds, such as those of Palermo and 

 Turin : in these a part only of the septal face is flattened and 

 drilled with very coarse foramina, the rest remaining slightly 

 gibbous and finely perforated ; whilst in many other varieties of 

 R. repanda the septal face is uniformly flat and pertused, for 

 instance R. Caribhcea, D^Orb., and R. pulchella, D^Orb. In R. 

 Auricula and its immediate congeners the whole septal face is 

 more or less convex and delicately porous. 



Some of these oblong varieties have been (as Professor Wil- 

 liamson has already noticed) erroneously grouped under the 

 genus Valvulina by D^Orbigny ; such as " V. scqualis," " V. ob- 

 longa," and " V. excavata." 



In var. a, the outline is more entire, and the chambers less 

 vesicular than in var. /3. These belong to a very variable group 

 of small elongate varieties of R. repanda. Var. a is intermediate 

 between R.Hauerii, D'Orb. (For. Foss. Vien. pi. 7. figs. 22-24) 

 and R. Brongniartii, D'Orb. {op. cit. pi. 8. figs. 22-24). Var./3 

 approaches very closely to Williamson's Rotalia oblonga (^lo- 

 nogr. pi. 4. figs. 98-100) ; the latter, which is larger but less 

 gibbous than var. /3, attains its finest development in the Eng- 

 lish Channel and the Bay of Biscay, at from 50 to 70 fathoms; 

 but similar varieties, though generally smaller, arc to be met 

 with in nearly every Foraminifer-bearing sea-sand or mud, at 

 variable depths, and are rather common in almost all Tertiary 

 deposits. 



28. Nautilus farctus. Page 64, pi. 9. figs. g-i. " Fossil : 

 Coroncina, near Sienna, Tuscany." 



The .shell here figured is essentially a plano-convex Rotalia ; 

 but in the further developments which varieties of this species 

 exhibit we have characters presented that make it very conve- 

 nient to divide the forms of this group (as well as those of an- 

 other Planorbulina, typified by Roaaliiia Poeyi, D'Orb.) from the 

 ordinary Rotalia-. For this subdivision the well-known name 

 Planorbulina is retained, which was used geucrically by D'Or- 



