430 CARBONIFEROUS LAMELLTBRANCHIATA. 



PI. XLIX, Hg. 1, is a beautifully preserved specimen in the collection of 

 Mr. J. Smith, of Kilwinning, showing the tuberculated markings on the anterior 

 part of the valve. Whether such markings occurred all over the valve or not I 

 am unable to decide, owing to the great paucity of specimens. 



All prior observers have considered that Allorisma Ansticei gaped. It 

 certainly did not gape in front ; and I am very doubtful if it gaped behind. The 

 shell was very thin, especially behind, and has been broken off here in all the 

 specimens I have been able to examine. The marked and characteristic byssal 

 sulcus and the absence of a byssal notch are noteworthy. Tellinomorpha {Chgeno- 

 mya) jucunda of de Koninck has certain points of resemblance with A. Ansticei ; but 

 it is much more gibbose, and has the byssal sulcus much less marked. Notwith- 

 standing the fact that the distribution of this species is wide, I regard it as very 

 rare. 



Genus — Tellinomorpha, de Koninch, 1885. 



CiiJEyoMTA (pars), <le Koninck, 1885. Ann. Mus. Eoy. Hist. Nat. Beige, vol. xi, 



p. 4. 

 Telltnomobpha, de Koninch, 1885. Ibid., p. 90. 



Generic Characters. — Shell equivalve, inequilateral, transverse, ovate. An- 

 terior side rounded, closed ; posterior side truncate, gaping. Hinge of the right 

 valve having a single cardinal tooth, with a socket on either side, in at least one 

 species. Pallial line entire ; escutcheon deep and broad, and much shorter than 

 the posterior part of the valve. Surface with irregular concentric undulations 

 and striae of growth, crossed by rows of small granules or tubercles. Shell thin. 



Observations. — The genus Chsenowija was established by Meek and Hayden 

 (1864) for certain shells from the coal-measures of North America, and was 

 supposed by them to embrace also certain Jurassic shells referred to Myacites. 

 The shells are said to be edentulous, but no figures of the hinge are given. The 

 posterior end is described as gaping, and a large but shallow pallial sinus is 

 noted and figured. In addition the authors state that all the species yet known 

 are also destitute of any traces of a shallow depression extending from the beaks 

 to the antero-ventral margin, so commonly seen in Myacites. 



Under tliese circumstances de Koninck was ill-advised to refer any of the 

 Belgian Carboniferous shells to Ghsenoniya ; for three at least, and possibly all 

 (four) species referred by him to that genus possess a well-marked sinus in the 

 neighbourhood of the junction of the anterior and middle thirds of the valve; all 



