44 



TYPE AMMONITES— VI Feb. 



Peronoceras, Hyatt, 1867. See T.A, i, (1911), v ; G.T., Ammonites 

 fibulatus, J. de C. Sowerby. Button-and-loop ornament, arched ribs on 

 subangulate venter. EL > > Li ; L2 pointed, subtrident. See T.A. 

 1926, PI. DCLXXXIII]. Upper Lias, [Cement Shale]. 



Similar species : Ammonites armatus ; Young & Bird, 1822, xiii, 9 ; 

 Am. turriculatus (Simpson), T.A. xxx ; Am. desplacei ; Dumortier, iv, 

 XXVII, 4 ; Stephanocerasfibulatum andrecs ; Wright, Lxxxv, 8 ; Peronoceras 

 preepositum, S.B., T.A. DCCL 



CoLLiNA, BonarelH, Boll. Soc. geol. It. xii, 1893, 13 ; Genoholotype 

 (only species figured) Collina gemma, Bonarelli ; serpenticone, pauci- 

 costate, arrow-shaped ribs on a bisulcate, medianly carinatiform venter. 

 (BonareUi's figure.) 



Catacceloceras, S.B., G.T., T.A., 1923, CDXIII, C. confectum, 

 S.B., North Nibley, Glos, grandis r,. ; EL> Li ; L2 unident ; all 

 lobes short. 



Similar species : Am. crassus ; Dumortier, iv, xxvii, 5 — 7, 10, 11 ; 

 xxviii, I, 2 ; Quenstedt, Amm. Schwab., xlvi, 19-21, 23 ; Stephanoceras 

 raquinianiim ; Wright, lxxxvii. 1-3 ; Coeloceras puteolus (Simpson) 

 T.A. LXL 



Orthodactylites, S.B., 1926, T.A. DCLIV ; G.T., 0. directus, 

 S.B., Middleton Cheney, Northants ; Upper Lias, Transition Bed ; 

 versirectiradiate. EL> Li ; si. simple. 



Similar species : Stephanoceras commune ; Wright, lxxxvii, 9, 10. 



Microdactylites S.B., 1926 ; G.T., M. attenuatus, (Simpson). 

 S.B., T.A., DCLV ; Peak, Yorkshire ; Upper Lias, Jet Rock. Hair-like 

 ribs arcuate over venter. 



Arcidactylites, S.B., 1926, T.A. DCLVH ; G.T., A. arctis, S.B., 

 Kings Sutton, Northamptonshire ; Upper Lias, " suhcarinatum." Ribs 

 fairly strong, arcuate over venter. EL> Li ; L2 very small, unident. 



Similar species : Am. holandrei ; d'Orbigny, cv, 1-3. 



ZuGODACTYLiTES, S.B., 1926, G.T., Z. braunianum, (d'Orbigny), 

 T.A., DCLVin. Northampton, Upper Lias, braunianum. Forewardly- 

 curved paired ribs (yoke-like) on subangulate venter [wh'ch may become 

 rounded] ; continuously subspinous on ventral edge ; [EL < Li ; L2 

 long, subtrident : all lobes well developed — d'Orbigny's figure, civ, 3]. 



Similar species: Am. braunianus ; Dumortier, iv, xxviii, 5. 



Postscript. Anguidactylites, p. 41. Add, as a similar species, 

 Dactylioceras delicatum (Simpson), T.A. DCLVL 



An analysis of the genera of Dactylioceratidae may now be given. 

 This could be carried further, even without touching the important point 

 of sutural differences. For instance, ' Costate ' obviously includes two 

 phases, (i) pre-tuberculate, (2) post-tuberculate. Some forms entered 

 as costate may, therefore, rightly belong to tuberculate, for they might 

 show tuberculation in inner whorls. Also degenerate tuberculation may 

 be overlooked because of its feebleness, or because of bad preservation. 

 The analysis will, however, show which genera come together in 

 similarity of ornament. 



