38 CARBONIFEROUS AMMONOIDS OF AMERICA 



ventral lobe is -oiig- and undivided. The external saddle is rounded, entire, 

 and shorter than the laterals. The first lateral lobe is serrated, four-pointed; 

 the second four-pointed; the third, three-pointed; the fourth, irregularly 

 three-pointed; the fifth, irregularly bifid. With the sixtli lateral lobe begins 

 the auxiliary series of goniatitic lobes, which are of irregular size, and eight 

 in number at maturity, growing smaller toward the umbilicus. These 

 characters could not be made ont distinctly on Miller's type, but the details 

 were clearly seen on No. 6474, from the same locality. The differences 

 between the two specimens might seem, at a casual glance, to be specific, 

 but closer study shows them to be due to difference of preservation, and to 

 different sizes at which the septa are seen. The type specimen shows the 

 keel at only a few places on the periphery, and so indistinctly that Miller 

 overlooked it, while No. 6474 shows the keel, 3i mm. liigh, entirely around 

 the periphery. On both specimens the body chamber is incomplete and 

 occupies a little over a fourth of the last revolution. It is not known what 

 was the shape of the a])erture, how long the body chamber was when the 

 keel began, nor what the internal lobes were like, since none of the speci 

 mens available sufficed to answer these questions. 



A smaller specimen, No. 6222, from the Kinderhook beds, of Burling- 

 ton, Iowa, showed nmcli simpler septa and the nari-ow angular abdomen 

 with the keel broken off'. It is undoubtedly in the beginning of the mature 

 stage of growth, and is of value in showing the shape of the cross section, 

 since the sides were free from the matrix. 



Occurrence. — At present there are known only five specimens of Pro- 

 dromites gorhyi, all from the same horizon, Kinderhook or Chouteau stage 

 zone of Aganides rotatorius of the Lower Carboniferous, equivalent to the 

 Tournaisian horizon of the Dinantian formation of Europe, viz: 



1. Miller's type, from the Chouteau limestone of Pin Hook Bridge, 

 Pettis County, Mo. No. 6208, paleontologic collection. Walker Museum, 

 University of Cliicago (Gurley collection). This specimen is the type of 

 the genus Prodromites Smith and Weller (PL XXIII, fig. 1). 



Dimermons. 



MiltimottTs. 



Diameter 114 



Height of last coil 64 



Height of last coil from the preceding 35 



Width of last coil 



Invokition 29 



Width of umbilicus 4 



