S8 THE NAUTILUS. 



In a large mimber of species, however, the apex is smooth and the 

 radial rihlets when prest'nt orifrinate below tlie apex. These are the 

 wide, ovate or subcircular specie.*, usually more or less depressed, of 

 whirii A. fvsctis may be considered the type. In these the apex is 

 blunt and smooth and the apical scar is not conspicuous. In A. pen- 

 tnsulce, however, the riblets in some sjieeimens seem to extend clear 

 up to the scar, but not info it. While in this respect this S])ecies 

 seems an exception to the rule, that the depressed s{)ecies have the 

 apical rejrion smooth, nevertheless its affinities are all with that group, 

 and in spite of the apparently intermediate character of its apical 

 sculpture, it seems better to class it with them. A similar tendency, 

 though much more feeble, has been observed in one set ot A. dia- 

 phanus. 



Tbe eastern American species, so far as examined, fall into two 

 natural groups characterized by their shape and contour as well as 

 this difference in apical sculpture. Pilsbry has already indicated 

 them (loc. cit.) on other grounds, atid it is interesting to find that 

 the distinction apparently also holds good on structural grounds of 

 some importance. 



The following list of eastern American species is arranged with 

 reference to their apical character: 



Apex striate. Apex smooth. Not examined. 



rivularls. fuscus. ohscnnis. 



tardus. diaplicums. elatior. 



parallelus. excentricus. calcariiis. 



sliiinekii. fiofdemani. horealis. 



filosus. eugraptus. ovalis. 



peninsulce. 



Any collector, who has any of the unexamined species as here 

 listed, will confer a fa\or by communicating with the writer. 



A NEW HAITIEN CHONDROPOMA. 



BY JOHN B. HENDERSON, JH., AND CHAS. T. SIMPSON. 



Chondropoma superhum. 



Shell having a small umbilicus, usually truncated, subsolid, some- 

 what shining; whorls 7, the two nuclear ones smooth and waxy; 

 those remaining in the truncated shell 4; sculpture consisting of 



