1926 



SYSTEMATIC 



named, in one of which, W. redudus, the decrease in length of lobe was 

 attributed to age (phj-logerontism). Subsequently a more aged species 

 of Wheatleyites was found, W. rarescens, which showed that the length 

 of lobe increased. About the same time a less advanced form, congruous 

 in suture-line with W. redudus, was discovered, to be named 

 Shotoverites pringlei. Obviously it is necessary to change Wheatleyites 

 redudtts to Shotoverites reductus (see below, p. 15). Table I, following, 

 shows how 4 specimens (3 species) of Wheatleyites agree in general 

 proportions of suture-line and how the two species of Shotoverites stand 

 together distinct from them. 



Table I— Wheatleyites & Shotoverites (Suture line, SI.) 

 Wheatleyites tricostulatus, CCCLXV 71, — , 60, 39-5 



W. opulentus, CCCLXXXIIIa 79, 56 ? 64, 31 ? 



W. „ , CCCLXXXIIlB 26-5, 66, 60, 38 



W. rarescens, DLXIa, 45, 69, 71, 45 



Shotoverites pringlei, DLXII 48, 40, 46, 22 



S. redudus, CCCLXXXIV 89, 39-5, 37 [43 ?] 24 



The length of Li in S. redudus seems to have been understated : 

 tested on the plate it gives 43 p)er cent. 



A similar instance of the necessity of taking the proportions of 

 suture-lines occurs in Dr. Neaverson's lately-published work (Amm. 

 Kimm. 1925). He makes a new genus Sphindoceras with genotype 

 S. crassum (li, i). This is a most remarkably longilobate species. 

 With it he associates 5. distans (iv, 3) of which he only gives suture-lines 

 of young stage — practically useless. But I have before me, from a 

 neighbouring brickyard, Mus. Pract. Geol. Collection, an adult specimen 

 of his species : it gives a lobation about 30 per cent, less than Sphinc- 

 toceras. Another genus Dr. Neaverson names Allovirgatites, genotype 

 A. woodwardi (in, i). He does not give the suture-lines at all clearly 

 of this or of other species of his genus, except A. versicostatus (p. 36, 

 fig. B. 6), though, obviously, the specimens show the suture-lines clearly. 

 But the deficiency can be supplied by examples collected by the 

 Geological Survey and myself from various brickyards in the Oxford 

 neighbourhood. The suture-line proportions are given in Table H : — 



Table H — Sphinxtoceras & Allovirgatites (Suture-lines) 

 Sphindoceras crassum, 11, i, 

 S. distans, M.P.G. Coll. 

 Allovirgatites woodwardi, in, i 



S.B. Coll. 

 „ versicostatus. Fig. B. 6, p. 36, 



, HI, 4 

 tutcheri, M.P.G. CoU. 



In these suture-line proportions Sphindoceras crassum stands out 

 quite alone, as an exceptionally longilobate form, surpassing even 

 Wheatleyites (see Table I, above), which has quite a good record in this 

 matter. Then all the examples of Allovirgatites yield proportions of 

 about 50 per cent, for EL and Li, both lobes being far shorter than 

 those of Sphindoceras crassum. The lobe-line of Neaverson's Sphinc- 



