Amplexus. MOLLUSCA. CEPHALOPODA. 251 



10. B. spinulosa " De{)ressed, undulations regulai-, every other one arm- 

 ed with two siiarp spines; ;opening elliptical; curvature very gradual;" struc- 

 ture obscure Sower. Min. Conch, t. ccxvi. f. 1. — Gree7i Sand, Blackdown. 



11. B. spiniger " Depressed; undulations many, slender; two rows of 



sharp tubercles upon each side, those nearest the front largest ; curvature 

 gradual." — Sower. Min. Conch, t. ccxvi. f. 2. 



12. B. Uiherculata "Depressed; undulations unequal, every third one 



largest, with two tubercles on each side, the lateral ones obscure ; curvature 

 gradual." — Sower. Min. Conch, t. ccxvi. f. 4, 5 — Clialk Marl, Folkstone. 



1 3. B. turgida " Depressed ; front irregularly swelled ; undulations re- 

 gular, disappearing over the back ; two rows of obscure tubercles near the 

 front ; curvature rather sudden." — Sower. Min. Conch, t. ccxvi. f. fi, — Chalk 

 Marl, Folkstone. 



14. B. nodosa. — " Nearly round, undulations regular; two rows of obtuse 

 tubercles upon the front, each tubercle placed upon two undulations ; aper- 

 ture obovate." — Sower. Min. Conch, t. ccxvi. f. 3. — Chalk Marl, Folkstone. 



15. B. plicatilis — " Slightly depressed, with numerous annular ridges ; two 

 rows of large, equal, flat tubercles upon each side ; curvature gradual. — Sow- 

 er. Min. Conch, t. ccxxxiv. f. 1 CImlk Marl, Warminster. 



Gen, amplexus. — Nearly cylindrical, divided into cham- 

 bers by numerous transverse septa, which embrace each 

 other with their reflexed margins. 



1. A. coralloides. — Tube irregularly bent, longitudinally striated; margins 

 of the septa deeply reflected, and regularly plaited. The septa seem to have 

 110 perforations. — Sower. Min. Conch, t. Ixxii — Transition Limestone, Cork. 



[The following extinct species in the genera Nautilus, Nummulita, and 

 Orthocera, are here added, having been omitted at their proper places at 

 pp. 229, 233, and 238.] 



1. Nautilus ej?joansMs.--Subglobose, umbilicated, finely striated ; lunbilicus 



small; sides of the aperture expanded Sower. Min. Conch, t. cccclviii. f. I. 



—Clialk Marl, Hanisey. 



2. N. biangulatus — Discoid, subglobose, with'a large umbilicus, and a keel 

 upon each side; front rounded. — Sozver. Min. Conch, t. cccclviii. f. 2. — In 

 Mountain Limestone, Bristol. 



3. N. globatns. — Subglobose, smooth, umbilicated ; ivhorls few, inner ones 

 concealed, rather flattened on the front, rapidly increasing ; umbihcus deep, 

 with an angular margin ; aperture very wide, arched, with a deejj sinus in 

 the front — Sower. Min. Conch, t. cccclxxxi. — Probalily my N. Wrightii is 

 identical with this species. — From Cork. 



4. N. multicarlnMtus — Discoid, subglobose ; inner whorls half exposed in a 

 large deep umbilicus ; edge of the umbilicus angular ; front compressed with 

 several carinse on each side the middle. — Soiver. Min. Conch, t. cccclxxxii 

 f. 1, 2 — Transition Limestone, Cork. 



5. N. carinatus — " Discoid, subglobose ; inner whorls half exposed, in a 

 large luiibilicus ; a keel in the middle of each side, and two ridges between 

 it and the flattened front." — Sower, t. cccclxxxii. f. 3 — Identical" with N. cr- 

 cavatHs alreadv described. 



