CLASS IV 



GASTKOPODA 



571 



In the Devonian of Bolieniia, Nassau, Ural and North America, great nnmhers of smooth, 

 circnLar, longitudinally striated tubes are occasionally met with, the posterior end of which is 

 inflated into a small Inilb. Similar tubes have also been described by Blankenhorn from the 

 Cretaceous of Syria. None of these differ externally to any great extent from Clio or Hiyliola. 



Vaginella Daudin (Fig. 1070, C). Shell long, ventricose, depressed 

 slightly caiialiculated and compressed laterally. Cross-section elliptical 

 Cretaceous to Recent. a h 



Gumerina Boas ; Trij^tera Quoy (Tihiella 

 0. Meyer). Tertiary and Recent. Euchilotheca 

 Fischer. Eocene. 



f^te 



SJ 



Fig. 1072. 



Family 3. Hyolithidae Nicholson. 



Shell symmetrical, conical or pyramidal, 

 straight or sharply bent ; cross-section triangular, 

 elliptical or lenticular ; one side often flattened, 

 and the other arched or with a blunt median keel. 

 Siorface smooth or with fine transverse striae, rarely 

 longitudinally striated or ribbed. Aperture com- 

 pletely closed by an operculum, the latter being 

 semicircular, triangular or lentiform, with lateral 

 nucleus, and concentrically striated ; pteropodia, . A, B, liyoUthes elegans Barr. Oidovician ; 



•,i 7 • , • J J j7 i ■ J (Etage D) ; Lodenice, Bohemia. Slightly ve- 



Wlth a chltmous support to the anterior edge. ^j,ced. C, H. maxima Ban-. Cambrian 

 Cambrian to Permian. (Etage C); Mleschitz, Bohemia. Anterior 



portion restored, with opercnUmi, and viewed 

 According to Holm the typical genus, ^anfie^'"' ''''^''' ^'^' -^' '-Operculum (after Bar- 

 Hyolithes Eichwald {Theca Sowb. ; Pugiuncuhis 



Barr.) (Fig. 1072), is divisible into two subgenera. One of these, Orthotheca Novak, 



contains forms with an abruptly truncated anterior end ; and in the other, Hyolithes 



s. str., the margin of the flattened side projects somewhat above the opposite wall. 



^^ ;. fi The forms known as Cleidotheca, Gentrotheca Salter, 



Gamerotheca, Diplotheca Matthew, Pharetrella, Hall, 

 Geratofheca and Bactrotheca Novak, fall within the 

 synonymy of Hyolithes. This genus is abundantly 

 distributed in the Cambrian, Ordovician and Silurian 

 of North America, Great Britain, Sweden, Russia and 

 Bohemia ; it occurs sparingly also in the Devonian, 

 (Jarboniferous and Permian. 



Pterotheca Salter ; Phragmotheca Barrande. Silu- 

 rian ; Europe. Matthewia Walcott. Cambrian. 



Fig. 1073. 



A, Tentnculitrs accdari.'^ 

 Schluth. Erratic block of 

 Ordovician age ; Berlin. C, 

 T. ornatus Sowb. Silurian ; 

 Dudley, England. C, T. 

 iLcnarltc^ Richt. Silurian con- 

 cretion ; Thuringia. A 

 smaller individual contained 

 within the larger (after 

 Novak). 



having a circular cross 

 embryo7ial bulb. Surface 

 portion of the shell often 

 Ordovician to Devonian. 



Suborder D. CONULARIIDA Miller and Gurley. 



Paleozoic forms of doubtful systematic fodtion, 

 resembling some Recent Pteropoda, but probahly to be 

 regarded as a parallel rather than as an identical 

 group. 



Family 1. Tentaculitidae Walcott. 



Thick - walled, tapering, elongate, conical tubes, 



section, and terminating posteriorly either acutely or in an 



ornamented with parallel raised transverse rings. TJie apical 



filled loith calcareous matter, or divided off by transverse sefta. 



