Oxynotieeran Series. 



The apparently wide divergence from the usual structure <>f the Arietidea 

 nted l>_v the hollow keel l.'.l me at li i -t to classify tins group as a distinct 

 family. The close affinities with the Axietidaa shown by the young, bov 

 and the intermediate characters exhibited by the agossiceran Beries render Buch 

 Gcation unnatural and undesirable 



of the keel and Battening of the abdomen in 1 1 1« ■ ol<l has do parallel 

 in the normal forms oi' the Arietid®, .-.> tar as known. 1 It must !»• remem- 

 bered, however, that thi* modification, together with it- correlative de< 

 in the lateral diameter of the whorl, is a fulfilment of the w 

 transformations. 



/',;•- S ■ — There are two subseries ; one, th ■ ' with 



oomparatively smooth shells, as in the leas involute and Btouter varietii - 



nd one, thi G rAt subseries, which has highly developed folds. 



of th( n tli<' am. unit of involution. The less involute I 



me what more in vol ut Oxyn. & still more involute 



ire parallel with '■ '■ iff, and 



I of the secon I A cording to mos( authors, \\<' could legiti- 



sider thai the first three were onlj varieties of one 



■ w would !>«■ willing t.> join the last three under one specific nam. I • 



raturi lults of the - series are ver) close together, reminding 



one of the approximate Butures in the oldest Btages of the individual in 



The pointed lobes and broad Baddies, the Bhort abdominal lobe and 

 long finger-like marginal lobes and saddles, remind us also of the Benile pecu- 

 liarities of the Butun I The ise in number of auxiliary 

 m-1 saddles and the general aspect of the sutures are, however, upon the 

 whole additional complications, and therefore progressive characteri* 



I gradations are uninterrupted from Greenowg) 

 ptions of the species Bhow that the principal diffi i 

 -• in th.> increasing involution oi and a correlatively 



ther and more compressed form of whorl. 

 Th. toium and G resemble closely the young "t 



I . no inter liate forms between the latter and 



- which would enabl le t<» verify this relation <>t" the younger 



Whethi 

 cannot be decided at present, owing to thi-< deficiency in the evidence; but that 

 both these form-' came from the same common stock, and that this stock was 



ible. 

 . the iif\t species of this subseries, bridges the gap between 

 nd 2 i I 



■how that this species must have been derived from G i, like 



! other terminal forms of series which have mark, 

 the smallest i"t m of its ow n ne. 



