254 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.52. 



The only specimen showing a portion of the cranial roof that has 

 thus far come to light is that illustrated in plate 2, fig. 2, which shows 

 theparietalsjfrontals and one each of the squamosals and postfrontals 

 in natural juxtaposition. The parietals are of about the same relative 

 length as in HolojHychius, and less elongate than in RMzodojJsis and 

 Onychodm; but further than this it is not possible to make compari- 

 sons, owing to the inadequate preservation of parts. Nevertheless, 

 being unique, the specimen is of importance for the bare hint it affords 

 of the arrangement of cranial roofing plates in this genus. Another 

 fragmentary head structure, to be interpreted probably as a portion 

 of the basisphenoid of this or some closely related form, is shown in 

 plate 7, fig. 5. 



Formation and locality. — Catskill (Upper Devonian) near Blossburg, 

 Pennsylvania. 



D. CARBONIFEROUS SYSTEM. 



ELASMOBRANCHII 



Family CLADODONTIDAE. 

 Genus CLADODUS Agassiz. 



Among the specimens of fossil fishes acquired by the United States 

 National Museum from Dr. G. Hambach, of St. Louis, is a series of 

 well preserved teeth of Cladodont, Petalodont, and Cochliodont 

 sharks from different horizons of the Mississippian section, and also a 

 number of interesting ichthyodorulites, some of which add to our 

 knowledge of established species. These are noticed in the following 

 paragraphs under their appropriate headings. 



CLADODUS SPINOSUS Newberry and Worthen. 



Plate 8, fig. 7. 



Cladodus spinosns Newberry and Worthen, Pal. Illinois, vol. 2, 1866, p. 22, 

 pi. 1, fig. 3.— E. B. Branson, 30tli Ann. Rept, Dept. Geol. Nat. Resources 

 Indiana, 1906, p. 1377, pi. 41, figs. 1, 2. 



The large, highly ornate teeth belonging to this species are of rare 

 occm-rence in the St. Louis limestone, and few perfect specimens have 

 been obtained. One which shows the characters of the base and 

 lateral denticles very clearly is catalogued imder the number 8104, 

 from the Hambach collection. It is the largest of any that have come 

 under the writer's observation, but unfortunately lacks the apical 

 portion of the crown. From the amended defhiition of this species 

 given by E. B. Branson I quote as follows: 



Teeth of medium or large size, broader than high; base representing a little more 

 than half of an imperfect hexagon, with the posterior side slightly longer than the 

 others; thick, with a sharpish edge behind, before strong beveled, and under scooped 

 out in a shallow sinus beneath the median cone; whole anterior border of base, above 



