1920 PERISPHINCTIDjE 



has kindly forwarded a sketch. The suspensive portion comes much 

 further down the whorl than that of Dichotomocems and the lobes are 

 more highly developed : like those of P. martclli, Siemir., p. 268, fig. 61. 



This selection makes Siemiradzki's " Formenreihe des Per. biplex" 

 (p. 256) the typical and perhaps only series of Perisphinctes. 



The result may be thus stated : — 



Family PerisphinctiDjE, Hyatt (see above, p. 26). Descendants 

 of coronates which in the catagenetic costate stage show parabolic curves 

 (intermittent zigzag ornament) and deep constrictions. Umbilicus 

 angulate, with fine ribs and constrictions [earlier, coronate cadicone, 

 skipped in later forms ?]. S.l. may become fairly complex. Parabolic 

 curves fail soon and constrictions may be ultimately lost. 



Genera, Perisphinctes, Dichotomocems, Grossouvria. 



Siemiradzki notices the angulate character given by constrictions to 

 the inner whorls of his Perisphinctes s. str. (p. 78) and compares it with 

 Morphoceras sculpture (p. 79) ; cf. Dichotomocems, CXXXIXc, 1 ; but 

 admits that the same character comes in small forms of the " subtilis- 

 Reihe " (p. 235), which, seemingly, has a coronate-cadicone origin — 

 the cadicone obvious but the coronate lost perhaps by brady-palingenesis. 



A Morphoceras origin is doubtful for many reasons — chiefly the 

 difference in position of furcation. Somewhat of the Morphoceratan 

 style required is shown by Vermisphinctes (PI. CLXII), but the lack of 

 parabolic curves prevents that coming into this family. 



The following corrections in nomenclature of species of Perisphinctes 

 s.l. have usually been overlooked, and it seems advisable to note them 

 here : — 



Ammonites triplicatits, J. Sowerby, 1815, M.C. I, p. 208, xcil, 2, 

 [Kimmeridgian, -post-virgula ?], " Portland Island, [Dorset]." 



Ammonites trifidus, J. Sowerby, 1821, M.C. Ill, p. 194, name given 

 to Am. triplicatus, J. Sowerby, 1821, M.C. Ill, 167, ccxcn and 

 ccxcni, 4 (non Am. triplicatus. Sow., 1815). Holotype, ccxcn, 

 "Pisolite formation [Argovian, c. martelli] near Malton, Yorkshire." 



Am. triplex, J. de C. Sowerby, 1835, M.C. VI, p. 249, name given 

 to the two specimens of Am. triplicatus, J. Sow. 1821 ; but, as the 

 holotype is already named trifidus, only the paratype is available. This 

 is from " Marly Limestone. . . .probably Calciferous Grit, ... .at Shotover, 

 near Oxford." A topotype, S.B.Coll. 2778, large adult, from Cowley, 

 (foot of Shotover Hill), near Oxford ; Lower Calcareous Grit — Argovian, 

 c. Goliathiceras ; S. 287, 21, 23.5 (22.5), 61.5. 



Perisphinctes, Waagen 1869, loc. cit. Genosyntypes, Planulates 

 of Middle and Upper Jura. Genolectotype, Ammonites biplex, J. Sowerby 

 1821, M.C. Ill, 168, ccxcni, 1 ; refigured, Miss M. Healey, 1904, 

 O.J.G.S. LX, 57 ; x ; Pal. U. 58. S.l. ornate, with long suspensive 

 part whose component lobes are fairly developed. Tubercle (or furcation 

 point) on edge of periphery, [just inside L 1 ] ; peripheral ribs not strong, 

 dichotomous in young [presumably tritomous in adult, before a stage 

 of massive ribbing is attained]. Proportions of Am. biplex (Dr. Lang) : 

 S. 46.5, 32, 33, 41 ; 120, 29.5, 29, 44 ; 160, 29.5, 24, 48.5. These 

 dimensions differ from those given by Dr. Siemiradzki (p. 267) chiefly 

 in the less thickness of the inner whorls, where there is displacement 

 and filling in by calcite : this would not be shown in a plaster cast. 



Dichotomoceras, S. Buckman 1919, T.A., III, Legend of 

 PI. CXXXIXa. Genotype, D. dichotomum. Like Perisphinctes as now 



