322 REPORT ON THE STATE CABINET. 



and allied genera, I do not mean to be understood as placing it without 

 reserve among the Terebratulidse : nevertheless this seems to be its 

 nearest relation, according to our present views of the classification of the 

 Brachiopoda. In thus placing it, I have written as follows {Palceonhlogij 

 of New York, Vol. iv) : " We had originally supposed that Tropidoleptus 

 would find its place among the Strophomenidse ; but there have been at 

 all times some important objections to placing it in this relation, while 

 later discoveries have rendered such a reference unnatural. Notwith- 

 standing the concavo-convex form, area, and large fissure under the beak 

 of the ventral valve, still the punctate structure of the shell and the 

 character of the crura seem to indicate its relations to be with the Tere- 

 bratulidge ; and T have accordingly placed it in an order following the 

 authentic genera of that family." 



In the ventral valve, the peculiarities lie in the strong crenulate teeth, 

 which are a little separated from the margin of the area (fig. 3). These 

 teeth are quite strong and thickened below, and their crenulate summits 

 are inserted into similarly crenulated teeth-sockets at the base of the 

 strong cardinal process of the opposite valve. In this valve, the divari- 

 cator muscular impressions are broadly flabellilbrm. The occlusor 

 muscular impressions have not been satisfactorily observed. 



The dorsal valve has a narrow area, and a wide and strong cardinal 

 process which nearly or quite fills the foramen of the opposite valve. 

 This process is often simple exteriorly, above the limit of the smooth or 

 striated pseudo-deltidium which covers it near the hinge-line ; but just 

 within the valve it is broadly grooved in the middle, usually with two 

 small deep pits just within the external smooth callosity, and on each 

 side there is a groove and accessory lobe, frequently not conspicuous. 

 The divisions made by the median groove diverge and terminate below 

 in obtuse processes which have some similarity with the bases of crural 

 processes in Orthis, but have more analogy with the Terebratulidaj. 

 These processes are sometimes clea'rly broken at their termination, but 

 are often smooth, as if the roughened surface had been cicatrized during 

 the life of the animal. Below these forks of the process there is a 

 narrow median crest or septum which reaches beyond the middle of the 

 valve, and sometimes nearly to the front. From the Umbs of the thick- 

 ened divergent processes there proceed slender crura which, at first 

 bending slightly outwards, send off a short spur into the ventral cavity 

 and are thence directed forwards, and gently curving, join the median 

 crest, to which they are attached, forming a loop of peculiar character. 



