300 MISS MCDOis'ALD a:n^d dr. tetteman o's [vol. Ixxvii, 



Procerithiinn Cossmann. Generally with, granular ornament. 

 Cerithinella Gemmellaro. Flat whorls, ornamented ^vith tubercles 



frequently forming- a band along the margin of the whorls. 

 Cryptaulax Tate. Five pronounced axial ribs, continuous from whorl 



to whorl, forming a tmsted pentagon. 

 Exelissa Piette. Spire pupoid, peristome detached. 

 Paracerithiiim Cossmann. Spire sub-spinous, whorls in steps. 

 Rhynchocerithmm Cossmann. Granular ornament. 



Cenacle Loxonematacea Cossmann. 



Family Loxoxematidje Koken. 



This family includes many of the sy)ecies which were formerly 

 referred to Chemnitzia. Aperture holostome, with a sinuous lip. 

 Typically with axial ribs. 



Zygopleura Koken. Sinuous axial ribs, no spiral ornament. 



Katosira Koken. Similar to Zygopleura, but with sj)iral ornament 



present. 

 AnoptycJiia Koken. Costate early Avhorls, smooth later whorls. 

 Hypsipleura Koken. Flat whorls, straight ribs. 

 Bigxucia Cossmann. With thick oblique plications in miny species ; 



form variable. 



Family Ccelosttlixidje Cossmann. 

 Shells more or less turriculate, with columella perforate. 

 Boiii-guetia Cossmann. With Turrifella-ioTm. 



Family Pseudomela^^iid^ Fischer. 



Smooth forms resembling the Melaniidse, but without a hetero- 

 strophic protoconch. Most of the Liassic species were formerly 

 called Chemnitzia. 



Family Mathildiidje Cossmann. 

 Turritelliform shells with heterostrophic protoconch ; holostome. 



II. TERMiyOLO&T. 



(A) Descriptive Terminology. 



Various authors have used descriptive terms in different ways^ 

 and there is some confusion in comparing the species which they 

 describe. This is particularly the case with terms relating to 

 ornamentation ; in Gastropods, as in Brachiopods and Lamelli- 

 branchs, costse of two types ma}" be deyeloped, either parallel to or 

 cutting the growth-lines, and it is necessary to state which tj^pe is 

 present.! It is frequently difficult to determine whether the 



^ This difficulty was appreciated by the late Ivor Thomas and Dr. F. J. 

 North in their work on Brachiopods, and they propose to restrict the term 

 ' costas ' to ornament transverse to the growth-lines. See I. Thomas, ' The 

 British Carboniferous Producti' Mem. Geol. Surv. (Pal.) 1914, pp. 225, 226 ^ 

 and F. J. North, ' On Syringothyris, &c.' Q. J. G. S. vol. Ixxvi (1920) p. 164. 



