REPORT OP THE STATE PALEONTOLOGIST 1902 



1231 



In Noetling's diagram, of which a copy is given on page 

 1229, it will be observed that coincident with these varia- 

 tions in the angle of obliquity is the passage from the Dim- 

 yarian into the Monomyarian divisions. This brief statement 

 of Noetling's determinations should be supplemented by the 

 reader with the perusal of the original paper or the English 

 abstract as cited. 



In elaborating the genus Lunulicardium which is so exten- 

 sively represented in the Intumescens zone of western New York 

 I have secured some very delicate barite replacements of the 

 valves of Lun. clymeniae which retain the protegulum 

 and give some indications of the value of torsion of the shell as 

 an ontogenic character and it has become possible also to 

 make some observations on the probable phylogenic significance 

 of the same feature. Lunulicardium has been commonly re- 

 garded as a bivalve with a long and wide byssal opening. Beus- 

 hausen has shown that the beaks in a certain subdivision of the 



genus (Chaenocardiola) to which Lun. clymeniae be- 

 longs are opisthogyre. We have, in a memoir on the Lamelli- 

 branchs of the Intumescens zone in New York, presented a careful 

 analysis of the generic characters but it here suffices to state that 

 the evidence supports the construction of the hiatus between the 

 valves as a byssal orifice while the umbo of the adult shell and the 



Fig. 1-4 Umbonal parts of Lunulicardium clymeniae showing triangular 

 area and the attitude of the prodissoconch with reference to the mature shell. The apex of 

 the larval shell is directed obliquely backward and its posterior end is the umbonal point of 

 the adult 



