108 
NATJTILOIDEA. 
Orthoceras reticulatum, Phillips. 
1836. Orthoceras reticulatum^ Phillips, Geol. of Yorkshire, pi. xxi. f. 11. 
Bp. Char. Shell straight. Section circular. Rate of increase 
rapid, about 1 in 4. Septa distant between | and ^ the diameter. 
Ornaments consisting of strong annulations which are distant about 
-| the diameter. The reticulate markings described by Phillips 
cannot now be made out upon the type specimen, which, however, 
may have lost a portion of its test since that author examined it. 
What remains of the test, which is probably the inner layer, is 
perfectly smooth. 
Remarks. This species comes very near in form and ornamentation 
(excepting the alleged reticulate markings) to 0. Koninckianum, 
d’Orb., but the annulations are more distant in the present species. 
Horizon. Carboniferous Limestone. 
Locality. Bolland, Yorkshire. 
Represented by the specimen figured by Phillips, and now in the 
“ Gilbertson Collection,” which was acquired by purchase in 1841. 
Orthoceras sulcatum, Fleming. 
1793. Orthoceratites .... superjicie sulcata, Ure, History of Ruther- 
glen and East-Kilbride, p. 306, pi. xvi. f. 2. 
1815. Orthocera sulcata, Fleming, Annals of Philosophy, vol. v. p. 202, 
pi. xxxi. f. 6. 
1815. Orthocera undata, Fleming, Annals of Philosophy, vol. v. p. 203, 
pi. xxxi. f. 7. 
1836. Orthoceras annulatum, Phillips, Geol. of Yorkshire, pt. ii. p. 239, 
pi. xxi. f. 9, ? 10 (not of Sowerby). 
1841. Orthoceras lineolatum, Phillips, Pal. Foss, of Cornwall, Devon, 
and West Somerset, p. Ill, pi. xliii. f. 209 h. 
1855. Orthoceras {Cyclocerai) undatum, M‘Coy, British Pal. Foss, 
fasc. hi. p. 574. 
1874. Orthoceras undatum, A'oung and Armstrong, Trans. Geol. Soc. 
Glasgow, vol. iv. p. 281. 
1876. Orthoceras undatum, Armstrong, Young, and Robertson, Cat. of 
the Western Scottish Fossils, p. 59. 
Bp. Char. Shell straight or slightly curved. Section a little 
oval. Rate of tapering about 1 in 5. Septa very convex, distant. 
Siphuncle almost exactly central. Surface marked with prominent 
more or less acute annulations, which have an undulating course in 
encircling the shell. The annulations as well as the spaces between 
them are covered with fine thread-like lines, of which there are 
