52 STOMATOPOBA. 



Bathonian Zone of Cosmoceras subfurcatum : Moselle (fide Terquem). 



Braun Jura: Balin. 

 Bajocian : Croizille and St. Vigors; Bayeux and Moutiers (fide D'Orbigny); 



Montvaux and Ars-sur-Moselle (fide Friren) ; ? Milly, near 



Ma9on (fide Ferry). 



Differences and Affinities. This species was originally figured 

 by Michelin as Alecto dichotoma. D'Orbigny recognized the 

 differences between the specimen used by Michelin and the type 

 form, and founded a new species for it. It is, however, nearly 

 allied to S. dichotoma. It forms a more open zoarium than does 

 that species, but this point is of little value. The main difference 

 between it and S. dichotoma is that the zocecia are pyriform. A 

 tendency to this shape occurs in some of the zooecia of S. dichotoma, 

 in portions of the colony where the zocecia are short and crowded. 

 The difference, however, appears to me to be of specific impor- 

 tance, for all the normal zocecia of S. dichotoma are regularly 

 cylindrical. Haime's type is now at Cambridge, and examination 

 of it shows that the peristome was raised. 



The young zooecia are longer and less pyriform than the older 

 ones. They have been figured by Walford as the var. attenuata. 



The representative of this species in the Cretaceous is S. plicata 

 (D'Orb.), 1 from the Cenomanian of Le Mans. In this, however, 

 the pyriform shape is still more marked, and the zocecia almost 

 become elliptical. The transverse ridging is reduced to a single 

 well-marked rib. 



As a Cainozoic representative of this species may be quoted 

 S, vesiculosa (Mich.), 2 from the Miocene of the West of Prance. 

 This agrees more closely with S. plicata than with S. dichoto- 

 moides, from which it may be distinguished by the almost 

 hippothoiform shape of the zooecia and the greater development of 

 the transverse rib. 



A species which seems to me to belong here is that described 

 by Haime as S. louchardi, from the Oxfordian of Boulogne. 

 Haime had only a very imperfect specimen, which he regarded as 

 a close ally of S. dichotoma. Brauns regarded it as a synonym 



1 Pal. fran9. Terr. cret. t. v. 1850, pi. ocxxix. figs. 12-15 ; 1852, p. 839. 



2 Alecto vesiculosa, Michelin, 1847, Icon. Zooph. p. 319, pi. Ixxvii. 

 fig. 3. 



