16 TYPE AMMONITES— III Mar. 



collection of the Geological Survey from Lydlinch, which is 3 miles W. 

 of Sturminster Newton, show about the zone required, c. scarburgense, 

 though examples of Sowerby's form are not among them. Lydlinch is 

 actually about 3^ miles from the Somerset border, and less than 2 miles 

 from the detached portion of Somerset around Holwell. So Lydlinch 

 may fit in well enough with Sowerby's location of Somerset : a small 

 mistake as to the run of county boundaries is easily made. 



England, (Foreign ?) ; Argovian 1. 



Vertebriceras g. n. The vertebrate group. Genoholotype, V. dor- 

 sale n. described below. Strongly carinate serpenticones becoming 

 massive, [almost sphaeroconic, then declining to platycones], periphery 4 

 with knotted keel, ornament 5**. Tuberculatum, (EL), OL l (S^V). 

 S.L., rather long and narrow L 1 , about equal to EL, L 2 short and broad. 



A series nearest to Cardioceras as now defined, but with a strong 

 keel on a broad, almost tabulate, subsulcate periphery. Ribs about 

 radial, but with strong sweep backward from contact-line over inner 

 margin, less strong sweep forwards on periphery [increasing in terminal 

 species]. Body -chamber about 3/4 whorl. Depressed area alongside 

 keel and on line of L l . 



This is the most ornate series of the Cadoceratida; : it does not 

 attain to anything like the swollen stage of some, but it is the most 

 massive of the distinctly carinate genera — attaining inflation of about 

 60 per cent. Early whorls of V. dorsale are polygyral smooth, indicating 

 a slowly-coiled serpenticone ancestor. (Vertumniceras and Goliathiceras 

 give evidence of similar stage). If a keelless platycone stage followed 

 this in the phylogeny, it is omitted ; and the serpenticonic stage is soon 

 obscured in massive species by the tachygenesis of swollen stage. 



England (Dorset, Berkshire, Oxfordshire). Argovian 6. 



The species of this genus seem to be lacking from Continental 

 strata — identifications of Am. vertebralis being incorrect. Card, dieneri, 

 Neumann (Oxf. Cetechowitz ; Beitr. Pal. Oest-Ung. XX, 1907, v, 16, 17) 

 has lateral aspect of Am. quadratus, but its fastigate periphery excludes 

 it from this genus. Its ribbing prevents association with Cardioceras 

 as now defined ; but it seems to range with Am. cordatus ; d'Orbigny 

 (Ceph. Jur. cxciv, 2, 3). 



In Argovian 1, associated with Cardioceras, are small specimens 

 with somewhat stout whorls of Vertebriceras pattern : they are not 

 forerunners — they lack the polygyral stage, and differ in other respects. 

 The species of Vertebriceras are large shells. 



V. dorsale n. Like Am. vertebralis, but whorls much less massive, 

 ribbing not so heavy, umbilicus wider. Tuberculatum and S.L. as above. 

 S. 80, 35, 42.5 (38), 39. Cowley, near Oxford ; Lower Calc. Grit, 

 arenaceous limestone ; Argovian 6 ; S.B. Coll. 2780, Holotype and 

 Genotype. 



V. vertebrate, J. Sowerby sp. 1817, (Min. Conch, II, 147, clxv ; 

 Miss Healey, Pal. U. 1905, 93). Proportions (Healey, fig. Ha), F. 56, 

 45. 59> 2 5 I 82, 39, 55, 31 ; fig. H., F. in, 35, T.41, F. 37.5 ; Univ. Mus. 

 Oxford Coll. From a quarry of Lower Calc. Grit on south side of main 

 road from Abingdon to Faringdon, 2| miles from the former ; between 

 the villages of Marcham, ijm. to S, and Dry Sandford, 1 m. to N. 



Chorotype, S.B. Coll. No. 3234, L. Calc. Grit ; Cowley, near Oxford ; 

 S 80, 36, 54, 30 ; 98, 36, 47(43), 32. 



V. rhachis n. Like V. vertebrate, but decreasing thickness and 

 expanding umbilicus earlier — decline from V. vertebrate ; ribs not so 

 coarse ; S. 80, 35, 46, 36 ; max. c. 90. Cowley, near Oxford, Lower 

 Calc. Grit, S.B. Coll. No. 2776 Holotype, 2777 Paratype. 



