238 CRETACEOUS GASTROPODA 
2. Burtinella, Morch, 1861, (Meerchia, Mayer, Journ. de Conch., Vol. VIII, 
p. 309). 
Burt. testa adulta libera, anfractibus primis in etate juniore affica, crassa, late- 
conico elevata, trochiformi sew planorbulari, plerumque sinistrorsa, rariter dextrorsa ; 
anfractibus gradatim ac regulariter crescentibus, interne tubulosis, externe aliquanto 
angulatis, striis incrementi tenuioribus atque fortioribus instructis ; ultimo ab ceteris 
sepissime dissoluto atque plus minusve prolongato, haud constricto ; apertura circu- 
lari, marginibus junctis, attenuatis. 
If the shells of Burtinella were free and litoral inhabitants, it is probable, that 
they had the end of the foot more of the shape of that found inthe Czcrpz, so as to 
enable them to move about. Judging from the section of the whorls of B. concava, 
(Pl. XVIII, Fig. 12), the shells are composed of three layers, of which the middle 
one is very thick, and the external and internal comparatively thin. The state of 
the fossil shells at my disposal does not admit of observing any difference in the 
almost homogeneous structure of these three layers. 
The genus has been founded on the Solarium Nystii, Galeotti (Vermetus id. 
Nyst., Polyp. Foss., Belg., II, p. 373, pl. 36, fig. 8). Except one doubtful species 
figured in Humphrey’s Conchology, pl. 10, fig. 8, all the others are known only 
in a fossil state. Mérch quotes only six species (three tertiary, two cretaceous, 
and one oolitic), which number will be increased considerably. The cretaceous 
species, as at present known, are— 
1. Burt. Sowerbii, Mant. (Sth. Downs, 1822, p. 111, pl. 18, figs. 14-15). 
2. Burt. subrugosa, Minst. (Goldf., Pet. Germ. I, pl. 71, fig. 1), is allied, if not identical, with 
the previous species. 
3. Burt. granulata, Sow. (Serpula id. Min. Conch., Vol. VI, pl. 597, fig. 8). Romer unites with 
this the Sp. erenato-striata, Miinster (Goldf. Pet. Germ. I, pl. 71, fig. 2, and Romer in Verst. Nord. 
Kreide., 1841, p. 102). 
4. Burt. Philipsii, Romer, (Verm. Sowerbit in Phill’s. Yorksh., pl. 2, fig. 29; Romer, loc. 
cit. p. 102). 
5. Burt. umbonata, Sow. (Min. Conch. Vermicularia id. I, p. 126, pl. 57, figs. 6-7), from which 
the Verm. umbonata in Mantell’s Foss. Sth. Downs, p. 111, pl. 18, fig. 24, looks not very different, 
though it has a smaller number of stronger and more distant transversal ribbings. 
6. Burt. concava, Sow., an Upper Greensand species, which is also found in our Sth. Indian 
deposits. 
7. Burt. conica, Hagenow, Bronn’s Jahrb., 1840, p. 666, pl. 9, fig. 15. 
8. Burt. trochiformis, Hagenow, ibidem, fig. 14. 
If any of the species with externally carinated whorls belong to this genus the following 
species will have to be added :— 
9. Burt. polygonalis, Sow., Min. Conch. VI, pl. 596, fig. 6. 
10. Burt. unilineata, Rom., Norddeutsch. Kreide., 1841, p. 102, pl. 16, fig. 2. 
ll. Burt. quinquecarinata, Romer, zbidem, fig. 3. 
The Planorbis radiatus, (Vermicularia, Lamck.), Min. Conch. II, pl. 140, fig. 5,) is a 
Helicocryptus, belonging to the family UmBontip 2, 
3. Stephopoma, Moérch, 1860. (Proc. Zool. Soc., Lond., 1861, p. 148). 
The shells, which belong to this genus, are generally very small, and usually so 
tender, as to be very rarely found fossil in a good state of preservation. Besides 
