Vol. 54.] DIVISIONS OE SO-CALLED •' JURASSIC ' TIME. 459' 



Genus Darellia,^ S. Buckm. 

 [Type : Darellia semicostata^ nom. nov.^] 



The costse are something between V-shaped and biarcuate in 

 curvature, and they are associated with a carinate-tabulate periphery. 

 The features of the periphery are similar to those of Hyperlioceras^ 

 but the rib-curvature is quite different : in that genus there is a 

 long peripheral projection. The features of the periphery distinguish 

 this genus from Graphoceras^ and so does the rib-curve. 



Specimens figured as the immature forms oi Hyperlioceras Walkeri^ 

 namely those depicted in pi. xvi, figs. 3, 4, 5 & 6 of the monograph 

 (pt. iii, 1889), are shown by their rib -curve to belong to this genus.r 

 They are generically and specifically distinct from Hyperlioceras 

 WaXkeri, and it is proposed to distinguish them as Darellia polita 

 ■^—separable from Darellia semicostata by a smaller umbilicus. 



In order to make the generic names which are used in the 

 genealogical Table (II) more intelligible and easier for reference, a 

 list of them is now appended, with certain illustrative species. 



YI. List of Genera arranged fnder Families. 



Opposite the generic names are placed the names of certain 

 illustrative species. In most cases the name which stands first may 

 be considered as the type-species. 



Family AMALTHEID^. 



Subfamily Am alt Heinle. 



Genus. Species. 



Amaltheus. margaritatus, nudus. 



Paltopleuroceras. spinatum, hawskerense. 



Subfamily SoNNiNiNiE. 



Genus. Species. 



Bajocia. Farcyi. 



Dorsetensia. Edouardiana. 



Haplopleuroceras. suhspinatum. 



Pcecilomorphus. cycloides. 



Sonninia. propinquans, Sowerbyi. 



WitcheUia. Iceviuscula. 



Zurcheria. Uhaldi, 'pugnax. 



Family AEIETID^. 



Genus. Species. 



Agassiceras. Scipionianum, Gaudryi. 



Arietites. Turneri. 



Arnioceras. semicostafAim, Hartmanni. 



Asieroceras. obtustim, stellare. 



Coroniceras. rotiforme, BucMandi. 



Oxynotoceras. oxynotus. 



1 In honour of Mr. Darell Stephens, F.G.S., to whose assiduous collecting in 

 the Inferior Oolite of the Sherborne district science is indebted for a knowledge 

 of many new species. 



^ Lioceras decipiens, var. intermedium Pj, Monogr. Palaeont, Soc. Inf. Ool 

 Amm.,' pt. ii (1888) pi. xii, figs. 10 &■ 11. 



