1884.] 



NATURAL SCIENCES OF PHILADELPHIA. 



53 



aaajjpij 



ON A CABBONIFEBOUS AMMONITE FBOM TEXAS. 

 BY PROFESSOR ANGELO HEILPRIN. 



Among a limited number of carboniferous fossils obtained 

 from the border of Wise County, Texas, and submitted to me 

 for examination by my friend, Mr. G. Howard Parker > a form 

 occurs which can unhesitatingly be referred to the family Am- 

 monitidse, and to the old genus Ammonites. Only a fragment of 

 a single individual of the form in question is to be found, and 

 this, unfortunately, has lost the shell, so that no external orna- 

 mentation, if any such existed, can now be detected. What 

 there is of the speci- 

 men, however, suflB- -^ 

 ciently indicates that 

 it was smooth, or des- 

 titute of ribs, and that 

 the decidedly globose 

 form was marked by 

 a strong involution of 

 the whorls, which ap- 

 pearalmost completely 

 embracing. The um- 

 bilical region cannot 

 be clearly made out. 

 The sutural lines of the 

 septa are very clearly 

 defined, and exhibit the ammonitic foliations in very nearly their 

 simplest expression. The lobes and saddles are numerous and 

 closely packed, the general appearance presented by them to the 

 unassisted eye being that of tessellation. 



The siphonal lobe is considerably' the largest, and is split into 

 two prominent tongues by the extension inwards of a deep sinus 

 having approximately the same width as the lateral prongs ; the 

 lateral prongs terminate each in two teeth, the inner one of which, 

 counting from the siphonal line, is somewhat longer than the 

 external ; the base of the lobal sinus produced anteriorly into 

 two acute sulci. The first lateral lobe terminates in two teeth, 

 the inner or siphonal one the shorter, truncated at the extrem- 

 ity, and sometimes exhibiting indications of apical division ; 



1. Fragments, natural size. 

 fled. 



2. Septal sutures, magnl- 



