INVERTEBRATE PALAEONTOLOGY. 47.") 



His diagram of one of the septa has two or three more of the smallest 

 inner Lobes than I have seen in our specimens; hut his figures <>l the entire 

 shell show the same number as in ours; and besides, I should not think this 

 a specific difference in shells agreeing so very closely in all other characters. 

 However this may be, I cannot believe that either arc identical with A. 

 Pierdenalis, von Buch, if we go to his typical figure for comparison, because 

 it shows distinctly on the larger half of the outer turn a row of compressed 

 nodes, arranged around each side near the periphery; these rows being also 

 represented around each side of the smaller part of the outer volution by a 

 ridge or revolving carina, from which the sides are abruptly beveled to 

 the periphery. Nothing of this kind, however, is seen on any of the speci- 

 mens of our shell, or those figured by Binkhorst. In addition to this, von 

 finch's figure shows his type to have 1 the septa lobes and sinuses much less 

 divided than they are in parts of the shell of the same size in our speci- 

 mens, or in those figured by Binkhorst. Again, von Buch represents the 

 siphonal lobe of his species as having merely two very short, closely approxi- 

 mate, hi- or tridentate branches, instead of being provided with two very 

 widely-separated, branching, terminal divisions. 



Dr. Binkhorst, however, seems to have made his comparisons rather 

 with a specimen sent by Mr. Schott from the Rio del Norte, Western Texas, 

 than with von Buch's figures of his type from near Fredericksburgh, farther 

 eastward, and possibly specifically distinct. The latter suggestion seems 

 also to receive some support, from the tact that Dr. Roemer figures another 

 specimen referred by him to A. Pierdenalis, from near the latter place 

 (Kreid. von Texas, pi. 1, tigs. 3, a, b, c), which, although of larger size than 

 von Buch's type, and agreeing in form with that figured by Binkhorst, still 

 shows the siphonal lobe to be altogether different in proportional size and 

 form from that of Binkhorst's specimens, as well as from ours, being very 

 decidedly smaller and merely composed of two diverging, contiguous, simple 

 divisions, that give it a cordate form. Roemer's specimen also shows the 

 lateral lobes much less deeply divided than in the Limbourg shell, or any of 

 our specimens of corresponding size. 



From the means of comparison now within my reach, I am, for the 

 reason already stated, unable to agree with Dr. Binkhorst in his identification 

 of his specimens with von Buch's species, and believe them to be identical 

 with the form here under consideration, which seems to me to be equally 

 distinct from the Texas shell described by von Buch. 



