1883.] 267 [Hyatt. 



specimens known. The funnels are as in Piloceras. We consider 

 this genus as still very uncertain, since there are not enough 

 forms known to characterize it properly, or make sure that it 

 did not have sheaths, and endosiphon. 



INCERTA SEDES. 



Tainoceratidae. 1 



We provisionally include in this group a series of genera which 

 appear to be affiliated by their forms, sutures, and style of orna- 

 mentation, though only a few of them are supposed to have 

 holochoanoidal siphons. The sutures have ventral lobes, and 

 no annular lobes until we reach the Mesozoic genera. The whorl 

 exhibits a tendency to grow away from the spiral, but this is 

 not constant and varies in the same species which may be gyroce- 

 ran, lituitean, or nautilian in its mode of growth in different 

 individuals, or varieties of the three first genera; the remain- 

 ing genera are more constantly nautilian. 



Trofcholites, Conrad, Hall, Nat. Hist. K. Y., Vol. 1, p. 192, 

 includes smooth or costated Silurian shells, whorl in section 

 depressed ellipse varying to quadragonal, siphon holochoanoidal, 

 and near the dorsum. Living chamber over one half of a volution 

 in length, with large ventral sinus, lateral sinuses inconspicuous 

 or absent and broad internal saddles. Sutures with ventral, 

 lateral, and broad dorsal lobes, without annular lobes, and some 

 specimens retain the straight outlines of the larva or have slight 

 dorsal saddles. Type, Am. Mus. N. Y. Siphon near the dorsum 

 or subcentral. This genus includes Troch. (Lituites) undatus 

 and angulatus, 2 Saem. Paleontogr., Vol. 3, and other smooth 

 shells with quadrate forms in section which have similar sutures, 



iThe first three genera appear to have holochoanoidal siphons, but these may be 

 really similar in structure to the siphons of Aturia, which misled even M. Barrande, 

 and the genera Enclimatoceras, Hercoglossa and Aturia certainly have ellipochoa- 

 noidal siphons. The absence of arcuate and gyroceran forms is also a notable 

 peculiarity. 



2 Lituites, Breyn, and Hortolus Montf. are founded upon species with entirely 

 distinct forms of whorls from either Trocholites or any of these genera. The young of 

 Lit. lituus. according to Lossen Zeit. Geol. Gesell, 1860, pi. 1, is compressed and 

 smooth. The genus appears to be represented i.i the Calciferous of this country by L. 

 Farnsworthi, Bill. Pal. Fos. Vol.1 , p. 21, fig. 24, and L. imper^tor, ibid, which have 

 similar whorls and siphon central. 



