PLEUROTOMARIA. 437 



angle. The body-whorl is relatively very large, subdiscoidal, and convex, forming 

 a blunt angle at the periphery ; this angle carries about three decussated spirals, 

 nodose at the points of intersection. The base is tumid, and largely excavated by 

 the funnel-shaped umbilicus ; strong spirals are decussated by sinuous radii not 

 extending quite to the margin. Aperture ovate-depressed. 



Relations and Distribution. — One of the most prominent features in this species 

 is presented by the radial costas of the flat part of the whorls, and this likewise 

 is characteristic of the other varieties of PI. Debuchii. 



My specimens are from the Murchisonse-zone of Chideock and Bradford Abbas, 

 and there are smaller ones, with a rounder basal periphery, from the Concavus-bed. 

 Rare. 



A micromorph closely resembling PI. platyspira, d'Orb. ( = PI. Debuchii, var. 

 platyspira, Deslongch.), occurs in the Murchisonse-zone at Crickley. 



378. Pleurotomaria mirabilis, Deslongchamps, 1848. Micromorph. Plate XXXIX, 



figs. 7 a, 7 b, 7 c. 



1848. Pleueotomahia mirabilis, Deslongchamps. Vol. cit., p. 31, pi. xvi, fig. 2. 

 1854. — — D'Orbigny, Terr. Jur., vol. ii, 



p. 433, pi. ccclvii. 



There are two specimens in my collection (one figured), which possess the 

 characteristic euomphaloid shape, sunken spire, wide umbilicus, and general orna- 

 mentation of this remarkable Middle Lias species. The ornaments on the upper 

 side present some difference, being finer and less nodose. The specimens are small, 

 the breadth averaging about 20 mm. Provisionally labelled PI. " submirabilis" ; 

 there is scarcely sufficient material for constituting a new species. Believed to 

 come from the Murchisonse-zone of Bradford Abbas. 



From the above it may be gathered that we have three Middle Lias species re- 

 appearing in the Murchisonse-zone, viz. PI. Mopsa, PI. platyspira, and PI. mirabilis ; 

 the two latter as micromorphs. 



379. Pleurotomaria subaraneosa, sp. nov. Plate XXXIX, figs. 1 a, 1 b. 



Description : 



Height (medium size) . . . .38 mm. 



Basal diameter . . . .45 mm. 



Spiral angle ..... 85°. 



