UrrEE TRIASSIC SPECIES. 125 



Greatest breadth of an imperfect entirely septate specimen, 2.82 inches; 

 convexity of same, exclusive of the nodes, 1.15 inches 



No entire specimens of this shell have yet been found; consequently 

 we cannot be quite sure whether or not the j)eriphery continues to be 

 rounded and costate on the outer volution of large mature specimens, 

 though it probably is at least rounded and less strongly costate. One dis- 

 torted specimen shows that near the broken larger end of the outer volution, 

 the costse become less prominent and more distant, with an intermediate one 

 between each two of the larger, the intercalated ones extending inward but 

 a short distance from the periphery, and dying out without coalescing with 

 the others. This part of the outer turn seems also to be nearly without 

 lateral nodes, which, however, are well developed on the inner turns of the 

 same specimen, where they are seen on the inner volutions just within 

 the inner margin of the umbilicus. None of the specimens are in a condi- 

 tion to exhibit very clearly the details of the septa; but the one represented 

 by our fig. 5 a, plate 1 1 , shows that there are three lateral lobes on each side, 

 the first or outer one being about one-third longer and wider than the sec- 

 ond, with, like the latter, a few short branches or mere digitations at the 

 end. The third or inner lobe is much smaller than the second, placed close 

 in at the inner margin of the whorls, and apparently provided with a few 

 short digitations. 



The position of the lateral nodes, it will be observed, varies somewhat 

 in different individuals; those on the specimen represented by fig. 4 being 

 placed nearly out at the middle of the volutions, while on that shown by 

 fig. 4 a they seem to be located farther inward. This, however, is probabl}^, 

 at least in part, due to the oblique distortion of this specimen. 



In relation to this species, Professor Hyatt sent the following note: 



" The development of this species is altogether anomalous. The whorls 

 were evidently cylindrical and smooth for a considerable time ; the increase in 

 size being at first very slow. Large tubercles appear while the sides are still 

 comparatively smooth in one specimen, though in another they have become 

 completely pileated. These tubercles are from the first very prominent. 

 Soon after the inti'oduction of these and the pilse, the increase in size becomes 

 much more rapid. The resemblance of the young to Lytoceras is very close 



