32 TYPE AMMONITES III Jan. 



J 92 J 



known as a Kallimorph — nomomorph, p. 6, refers only to size, 

 not to standard condition in shape and ornament ; that which is nod 

 normal, kakomorph, This requires subdivision : a form awry in 

 shape, pJagiomorph (n-Xayios, crooked) ; a form with ornament 

 awry, distorted ribs; loss of keel in a carinate or like defects, or with 

 exaggerations, any disturbance of ornament due to injury or disease : 

 dysmorph (PI. CLXXXVIII). Dysmorphy in youth may be recovered 

 from, to show a kallimorph old age, or a kallimorph youth may receive 

 injury and become a kakomorph adult. As Gastropods and Turrilites 

 show, plagiomorphy may become the standarized form : then it is really 

 kallimorphy and further chance departure from that standard would be 

 required to constitute plagiomorphy. The Turrilites of the Cretaceous 

 are not truly plagiomorphs, but the so-called Turrilites of the Lias arc. 



For a study of malformed or cripple Ammonites see Engel, Ueber 

 kranker Ammonitenformen im schwabischen Jura ; Nova Acta Ksl. 

 Leop.-Carol. Deutsch. Akad. Naturf. LX1, (5), 1894, 327. 



A further term is required for a shell which has undergone deforma- 

 tion during fossilization : allomorph (2XXm, other than what it is, 

 untrue). Gracilisphincks gracilis, PI. CXCIII, is an allomorph, its shape 

 altered by compression. 



Systematic 



Family PROPLANULITIDJE, nov. 



Heavy ribs in and around the umbilicus suggest a zigzag origin ; 

 but style is different — stoutest part near inner, instead of towards outer 

 end ; and its persistence, through serpenticone and into platycone ; 

 also V is nearer inside — about on L2 instead of nearly on Li ; while 

 the s.l. is far less developed. Species with these characters may be 

 surmised to have a coronate (Teloceratan) origin and to fall between the 

 families Zigzagiceratidse and Pachyceratidse — s.l. much less developed 

 than that of the first, rather more developed originally than that of 

 the second, but quickly falling into a very degenerate condition : in the 

 well-developed stage there is a spreading (palmate) ending to Li which 

 is very characteristic. In Pachyceratida? the teloceratan (cadicone) 

 stage is long retained, and there is little falling away from it ; in 

 Proplanulitida; there is rapid falling off into compressed serpenticones, 

 even platycones, with narrowed periphery, little sign of cadicone and 

 only heavy ribs as relics of teloceratan stage : even these suffer — in 

 some Proplanulites there is much delay in their appearance, presumably 

 the phenomenon of bradypalingenesis. The length of Li in proportion 

 to breadth of whorl appears, at any rate in this family, as a useful guide 

 to genera and to series within genera. This may be stated thus : Li at 

 47 mm., 42 per cent. When, in illustrations, s.l. has been traced, the 

 length of guide-line is greater than breadth of whorl by the amount 

 of the gibbosity of the whorl — a reduction will have to be made before 

 stating the result : the greater the gibbosity the greater the reduction. 

 In s.l. reproduced from a photograph no correction should be required. 

 The measurement of Li is made from the end of the terminal lobule 

 up the middle to a line joining ES and Si. Where one saddle is deeper — 

 more produced — than the other, the cross line may run obliquely. 

 Up to a certain point the length of Li should increase ; afterwards, 

 as the whorl loses gibbosity and increases its breadth proportionately 

 to diameter, the length of Li would decrease. In aged specimens the 



