CATULLOCERAS DUMORTIERI. 
277 
furrow, and so resulting in Gatull. Ferroudi^ and the other branch replacing the 
ventral furrow by a small carina in a flat area, Gatull. BumorUeri, — or whether 
Catiiil. Perroudi is only a form in which the nascent furrows beside the carina of 
Gatull. Dumortieri have become more specialized, cannot be stated until more be 
known concerning the exact horizon of Gatull. Perroudi — if it be an earlier species 
than Dumortieri. 
Catulloceras does not differ greatly from the less-developed forms of 
Dmnortieria, D. prisca, &c., except that these species show by their ribbing a 
difference in ancestry (p. 232). It is needless to look for much difference in 
Gatulloceras and the lower Dumortierige just at the time of divergence. The more 
specialised forms Dum. striatulo-costata, radians, Moorei, &c., with their Gram- 
moceratan-WkQ aspect, differ in shape of whorls, ribbing, and their general 
involuteness and compression. 
The species of this genus are all scarce, and the material I have to deal with 
very scanty. In this country there are four species, namely, Cafull. Dumortieri, 
Catidl. Leesherr/i, Catull. insignisimile, and Gatull. aratum. 
Catulloceras Dumortieri [Thiolliere) . Plate XXXIX, figs. 6 — 9. 
1855. Ammoi^ites Dumortieri, v. Thiolliere. MS. (teste Duniortier.) 
1874. — — Dumortier. Depots Jurassiques Bassin du Rhone, 
iv, pi. Ivii, figs. 3, 4. 
1885. Harpoceras Dumortieri, Haug. Beitr. Monogr. Harpoceras ; Neues 
Jahrbuch fur Mineral., &c., Beil.- 
Bd. iii, p. 664. 
1886. SiMOCERAS Dumortieri, Vaceh. Oolithe Cap san Vigilio ; Abh. der. k.-k. 
geol. Reich sanstalt, Bd. xii, pi. xxi, 
figs. 11—14. 
1886. Harpoceras elmagum, de Qregorio. Foss. de Valpore ; Annales de Greol. 
et de Pal., 2 Livr., pi. i, fig. 3. 
p. 7. 
1887. Dumortieria (Catulloceras) Dumortieri, Haug. Ueber die Polymor- 
phidse ; Neues .Tahrbucii fiir Mineralogie, 
Bd. ii, pi. V, fig. 6. 
Discoid, evolute, carinate. Whorls numerous, nearly circular, the sides very 
gibbous, ornamented with direct ribs slightly inclined laterally and ventrally. 
Ventral area broad but ill-defined, somewhat flattened in the middle, and divided 
^ Dumortier et Eontannes, " Descr. Amni. ; " ' Memoires de I'Academie de Lyons,' t. xxi, pi. iii, 
fig. 8, 1876. 
