4IO NEWTON : MOLLUSCAN REMAINS IN ENGLISH KEUPER. 



ventral margin curved and ascending soon after passing the 

 umbonal axis ; posterior line runs obliquely from the umbo ; 

 ornamentation consists of concentric furrows, more or less ob- 

 scure on the central and umbonal regions, but distinct else- 

 where ; one more prominent than the others near the ventral 

 margin probably indicates the position of the pallial line. 

 There is an absence of radiating striae. 



Thracia (?) Brodiei. 



Fig. I. 



(Nat. size). 



Observations. — Great difficulty is felt in assigning this 

 impression to any particular genus, but taking into account the 

 preponderance of its anterior region, the possibility of an 

 attenuated posterior end as suggested by the obliquity of the 

 posterior line and the rather rapidly ascending ventral margin, 

 together with the fact that the original shell structure was of a 

 most delicate description as evidenced by the distinctness of 

 the concentric markings, we may venture to regard it as l)elong- 

 ing to the family of the Anatinid^e and most possibly to the 

 genus Thracia. It may be recognized, at any rate, provisionally, 

 under the name of Thracia (?) Brodiei. 



Another species of this genus, mostly found as casts, called 

 Thracia mactroides Schlolheim' sp., has been recorded from 

 the Muschelkalk and Keuper strata of Germany, but there 

 appears to be no need to confound it with the British form, 

 which is anteriorly deeper in contour, generally larger, and with 

 the umbo directed rather more posteriorly. 



1 ' Nachti-age Petrefactenkunde,' 1823, part 2, pi. 33, fig. 4, p. 109. 



J.C., vii., July 1894, 



