R. B. Newton — On Trematonotus . 339 



of tlie Haliotidee, and by this classification he at once added a far 

 greater antiquity to the family than had hitherto been accorded it. 

 This position for the genus would appear to be the most natural one 

 that could be suggested, since we may fairly assume that the open- 

 ings on the dorsal surface would, during the life of the mollusc, be 

 used for the ejectment of foecal matters and for supplying the 

 branchige with water, as is known to be the case in the existing 

 Haliotis. Some interesting observations on this feature of the 

 recent genus were published a few years ago by Mr. Edgar A. 

 Smith ^ when recording a species of Haliotis exhibiting the abnorm- 

 ality of two rows of perforations. In his remarks he gives the 

 position of the anal and branchial regions as immediately beneath 

 the orifices. 



Since the publication of the second species of Trematonotus, in 

 1875, nothing further respecting its history has appeared ; and it 

 is hoped that a notice of its occurrence elsewhere may prove a 

 subject of considerable interest to the palfeontologist. 



The new material suggesting this communication consists of two 

 well-marked shells, which appear to be referable to this genus, and 

 belonging homotaxially to the same horizon as the American species, 

 having been obtained from the Wenlock Beds, in the neighbourhood 

 of Dudley. They originally formed part of the celebrated " Johnson 

 Collection," now in the possession of the Geological Department of 

 the British Museum. 



Professor Hall's rendering of the generic name was Tremanotns ; 

 but through an inaccurate compilation of that word Dr. Paul Fischer 

 has made it the occasion of an alteration, and it now appears as 

 Trematonotus? The original diagnosis stands as follows : — " Volutions 

 apparently in the same plane ; umbilicus on both sides ; aperture ex- 

 panded ; the dorsal line pierced by several oblong perforations." 



Trematonotus Britannicus, n.sp. 



Specific characters. — Shell symmetrical, discoidal, cordiform, with 

 few volutions ; umbilicus obscure; dorsal surface narrow near spiral 

 region, then suddenly expanding, convex, thinning out towards 

 margin with a gradual reflection ; central ridge composed of slightly 

 raised elongate perforations which cease after extending to about 

 three-fifths the length of the shell ; ornamented with rather closely- 

 set wavy strite, running parallel to the central ridge, which are 

 directed outwards as they reach the expansion, and marked trans- 

 versely with several ai-ched lines of growth. The ventral surface 

 shows a much expanded aperture, wedged in which is the elliptically- 

 shaped whorl containing the inner volutions ; this whorl bears traces 

 of the perforations which are probably more or less filled up ; the 

 body-chamber is cordiform and deep and is bordered by a wide and 

 spreading lip which is thin, slightly convex, and ornamented with 

 oblique radiating striee ; aperture entire. 



Dimensions. — Height = 90 mm.; width (maximum) = 65 mm. ; 



1 Annals, 1888, pp. 419-421. 



2 Manuel Conchyl. 1885, p. 854. 



