328 M. K. A. Zittel on Fossil Lithistidce. 



transversarius) of the Cracow district ; but these belong chiefly 

 to undescribed species. In the Swabian and Frauconian 

 specimens the most distinctive characters have been destroyed 

 by the process of fossihzation and subsequent weathering, so 

 that many of them are undeterminable. 



All the species occur in the Upper Jura : — 



*1. Hyalotragos {Tragos) patella y Goldf. v. 10 & xxxv. 4; 

 Quenst. Petr. cxxviii. 26-28, cxxix. 1-3. 



2. ? Tragos radiatum^ Goldf. xxxv. 2 ; Quenst. Petr. 

 cxxviii. 24, 25. 



3. Tragos reticulatiim, Goldf. xxxv. 5 ; Quenst. Petr. 

 cxxix. 10-15. 



4. Tragos mfrajugosum, Quenst. ib. cxxix. 6. 

 *5. Tragos rugos^im, Goldf. xxxv. 4. 



6. Tragos pezizoides, Goldf. v. 8. 

 Tragos Jistulosu7n, Quenst. Petr. cxxviii. 15-23. 



Pykgochonia, Zitt. 



Tragos p. p., Goldf., Quenst. 

 Forospongia p. p., D'Orb., Pom. 



Sponge cup -shaped, on both sides with margined verruci- 

 form very shallow oscula. Skeletal structure and canal-system 

 as in Hyalotragos ; vertical tubes but slightly developed. 



The typical species {Tragos acetahulum, Goldf.) was re- 

 ferred by D'Orbigny to Forospongia ; but as this name em- 

 braced forms belonging to various genera, and the diagnosis, 

 " Spongiaire lamelleux ou cupuliforme, cribl^ de pores des 

 deux cotds,^' is better suited to half a dozen other genera, it 

 has been dropped. Rubbed specimens of this Upper- Jurassic 

 genus may easily be confounded with Hyalotragos. Species : — 



1. Pyrgochonia [Tragos) acetabulum^ Goldf. v. 9; Quenst. 

 Petr. cxxix. 7, 8, 18. 



Tragos infranudatum, Quenst. ib. cxxix, 6. 

 Tragos verrucosum, Goldf. xxxv. 6. 



DiSCOSTROMA, Zitt. 



Tragos p. p., Quenst. 



Sponge disciform or flat funnel-shaped ; upper surface con- 

 vex, with crinkled pits and elevations, and with a central 

 cavity, sometimes narrow, but rather deep. Skeleton and 

 canal-system as in Hyalotragos. Only in the Upper Jura. 



1. Discostroma {Tragos) intrlcatuniy Quenst. Petr. cxxix. 

 20. 



