"nl asco Sai sent a 
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4 
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SECOND, OR SCHLOTHEIMIAN BRANCH. 127 
and in Volume II. he figures Wek. extracostatum, Plates XIV., XVI., and Panznert, 
Plates XV., XXI. The figure of eatracostatum shows an old whorl which is acute, 
but not involute. Among discoidal shells, Wek. circacostalum, Plates XV., XV1., 
curvornalum, Plate XVI., and haploptychum, Plate XVII., show that the whorls of 
their earlier nealogic and adult stages are without channels. Wek. anisophyllum, 
Plate XIX. Fig. 1 a, shows a very old stage with subacute trigonal whorl, and 
pile replaced by folds. Woh. megastoma, Plate XVIII. Fig. 2, 3, shows ear- 
lier nealogic stages with pile continuous across the abdomen in the adult and 
senile stages. Woh. euplychum, Plates XVIII., XX., stenoptychum, Plate XX., 
latimontanum, Plate XX., and diploptychum, Plate XXL., also belong to this ge- 
nus. The last two are senile specimens, with subacute outer whorls, and all 
the above are discoidal shells exhibiting transitions from Psiloceras to Schlo- 
theimia. 
There are, however, involute forms in this series also figured by Wihner in the 
same work, but in Volume IV. These are Wek. Guidow, Plate XXVI. Fig. 3 a, b 
(not Fig. 7), and Woh. Emmrichi, Plate XXVI.' We 
doubt whether either of these involute forms can 
be regarded as transitional to Schlotheimia, as sup- 
posed by Wiihner. 
The results of our work upon the nealogic 
stages and their meaning in Schlot. catenata, and all ped of 
other species, show that series arose only from dis- Rye. 20-22. — Views from in front, 
coidal shells, and probably never originated from Dadsiae ates Willie std he te 
the compressed and involute forms. These are involution of this species. The charac- 
themselves invariably discoidal and less compressed Ghee spent De ee ss 
° genus are also noticeable in these 
in their own young, showing them in every case figures? 
to have been derived from shells having depressed abdomens and discoidal 
whorls. 
Canavari, in his “ Unteren Lias von Spezia,” ® describes and figures dwarfs or 
the young of Wek. (Aigoc.) Emmrichi under the name of Guidoni. Wiihner thinks 
that Canavari’s forms (Plate XVIII. Fig. 14, 15) are referable to his Guddon’, and 
Fig. 16 to be identical with his Kmmrichi. The last is to us a very remarkable 
form, since it possesses continuous lateral and abdominal constrictions. 
SCHLOTHEIMIA. 
The form varies in this genus from discoidal to involute, but the umbilici are 
never entirely covered in. The whorls are usually flattened more or less on the 
sides, and the abdomen depressed. In the nealogic stages this form is common, 
1 We have given outline figures of Wah. curviornatum, Summ. Pl. xi. fig. 7, haploptychum, fig. 8, toxo- 
phorum, fig. 9, and Emmrichi, fig. 10. 
2 This figure, according to Wahner, is poorly drawn, the last volution too narrow, the umbilicus too 
open. It, however, exhibits the general aspect of involute forms in this series, and we have retained it 
with that purpose in view. 
8 Paleontogr., XXIX., and Mem. del. Carta Geol. d’ Italia, III, 1888. 
