SPHENODISCID ®. 65 
sides. Unluckily the antisiphonal lobe was not exposed by excavation, 
and therefore it was not considered necessary to draw these curves. This 
species is very instructive, since its external characteristics are well marked 
and they show that the amount of involution, the general outlines of the 
lobes and saddles, and the number of divided saddles remain very con- 
stant, while the trifid or bifid outlines of the larger saddles are variable. 
These minor details of the saddles, and of the lobes also, depend on the 
relative growth of marginals and may vary at different stages of growth 
or on the opposite sides in some individuals or in different individuals. 
The number of septa may also greatly vary, thus in Bohim’s and the fossil 
figured on Pls. III and V they are 5 mm. apart near the center; in Braun’s 
they are 9 mm. distant at about the same age and the saddles are much 
longer. 
Another specimen from the same collection is given on PI. VI, fig. 6, 
and this although closely associated with S. lobatus, and apparently at first 
sight the young of that species, has all the external characters and the sutures 
of pleurisepta. The fossilization is in the peculiar yellow limestone, with 
iron incrustations of the specimens of Jobatus from the same locality. It is 
of course possible that this specimen may be the young of lobatus, which I 
have never seen of as small size, but in any case it is identical with plewrisepta of 
the same age, which has an acute venter on the outer volution and sutures 
like those of Pl. III, fig. 15. There are five bifid saddles on the right side 
at the point where that side is about 30 mm. broad, and on the left side, 
where 20 mm. broad, the fifth saddle shows the faintest possible beginning 
of a median marginal division. 
Locality: Near Laredo, Rio Pecos, and near Eagle Pass, Tex.; Brooks- 
ville, Noxubee County, Miss.” 
Age: Eagle Pass beds, Upper Cretaceous. 
«The following note was contributed by Mr. Stanton: 
“Tt is pretty well established that Conrad’s specimens were not collected near Laredo. It is 
probable that they came from the neighborhood of Eagle Pass, where the species is abundant. It has 
been collected by Geological Survey parties from localities from 1} to 18} miles southeast of Eagle 
Pass. 
“<T doubt whether the species has been found on the Rio Pecos. There are certainly no beds that 
could have yielded it near the mouth of that stream.” 
MON XLIV—035 5) 
