J, W. Jackson^^The Brachiopod Liothyrella. 73 



. Exposures of the clays above the Plungar ironstone are rare, and 

 such as still exist are not veiy lielpful. A brick-pit south of Brant 

 Broughton shows 10 feet of fine-textured sandy clay, -with fossils 

 indicating the o:rywoi(Mm zone ; another pit near the canal at Wools- 

 thorpe shows similar clays which were thouglit by the Survey ^ ta 

 represent part of the Jamesoni zone. A disused biick-pit south-east 

 of Bassingham in 1916 showed the following succession : — 



ft. in. 

 Marly clay with Pleuromya ...... 1 



Yellow raggy limestone with Belemnites . . . . 16 



Clay 6 



Such fossils as were found confirmed the Survey's conclusion that 

 these beds should be assigned to tbe armatum zone.- 

 {To he concluded in the March Number.) 



IV. — On the New Brachiopod Genus, Liotbyrella, of Thomson. 

 By J. WiLFRiB Jackson, F.G.S., Assistant Keeper, Manchester Museum. 



THE new genus, Liothyrella, has recently been created by 

 Dr. J. Allan Thomson^ for the reception of a series of recent 

 and fossil Terebratulids commonly ascribed to the genus Liothyrina. 

 The chief characters upon which the genus is founded are the 

 presence of fine radial ribbing on the surface of the shells and the 

 possession of a short, low, thin, mesial septum in the dorsal valve. 

 In tlie thickness of the shell, Liothyrella is said to stand between 

 Liothyrina (genotype L. vitrea) and Terehratula, sensu sir., all three 

 genera being finely punctate. Tiiomson takes the recent Magellanic 

 species .i. tiva (Brod.) as the genotype of Liothyrella, and includes in 

 the same genus L. uva, var. notorcadensis, Jackson,'* from Scotia Bay, 

 South Orkneys, and a new species dredged off Tasmania by the 

 Mawson Expedition, as well as two Australian Tertiary species, 

 Terehratula tateana, Tenison- Woods, and T. concentrica (Hutton). 

 He remarks that "probably also manj^ of the other southern 

 species ascribed to Liothyrina will be included here, but the 

 descriptions do not state whether or not a mesial septum is present" 

 (op. cit., p. 44). 



The excellent researches made recently by Thomson upon the 

 morpholog}" and classification of the Brachiopoda are to be highly 

 commended, as they have led to some remarkable discoveries being- 

 made in connexion with New Zealand Tertiary species. Though 

 agreeing in the main with his conclusions regarding some of the 

 groups with which he has recently dealt, I feel compelled to dissent 

 from him with regard to the proposed division of the Liothyrina on 

 the lines defined. My own researclies, extending over several years 

 and embracing numerous recent and fossil species, have led me to 

 offer the following observations. 



^ A. J. Jukes-Browne, Geology of South-West Lincolnshire (Mem. GeoL 

 Surv.), 1885, p. 32. 



2 W. H. Dalton, Geology of Lincoln (Mem. Geol. Surv.), 1888, p. 21. 



^ Trans. N. Zeal. Inst., vol. xlviii (1915), p. 44, 1916. 



'' Jackson, "The Brachiopoda of the Scottish National Antarctic Expedition" : 

 Trans. Boy. Soc. Edin., vpl. xlviii, pt. ii (No. 19), p. 375, pi. i, figs. 1-3, 1912. 



