304 PALEONTOLOGY OF NEW YORK. 



vergent, slender jugal processes are given off not far from the origin of the 

 lateral lamellae. The scars of the adductor muscles are situated just in front 

 of the cardinal process on either side of the septum, and are not clearly 

 delimited. 



Shell-substance highly punctated in all its parts. 



Type, Strophomena carinata, Conrad. Lower and middle Devonia)i. 



Observations. The original determination of the characters of Tropidoleptus 

 led to its assignment with the terebratuloids. Presumably on account of its 

 external expression, systematists and other students have generally been un- 

 willing to admit this determination, placing the genus preferably among the 

 strophomenoid and leptsenoid genera. After the examination of a large amount 



.i^^^^^i-^-^ 



Fig. 227. Fig. 238. 



Tropidoleptus carinatus, ConiaJ. 

 Fig. 2-27. The interior of the brachial valve; showiug the^cardiiial process, creuulateil ilental sockets, loop and raeiliau 



septum. 

 Fig. 228. The same in profile; showing the height of the median septum and the mode ol" attachment of the lamella; of 

 the loop. 



of material, representing the various growth-stages of the shell from a 

 size less than 2 mm. in diameter to maturity, and having reviewed all 

 the points involved in the original account of the brachidium, these have 

 been found to be correct in every particular. In no observed condition 

 of growth does there exist a deltidium on the pedicle-valve, and hence it 

 becomes necessary to recognize Tropidoleptus as a terebratuloid genus, unique 

 among the palaeozoic brachiopoda. 



