1887.] 217 fCope. 



which terminates abruptly. Shallow grooves separated by ridges radiate 

 from this prominence in all directions. On its sides the sculpture becomes 

 smaller and more irregular. In the second type of bone, the median keel 

 is elevated into a crest which extends the entire length, and cannot be 

 distinguished at any point as a knob. The section of such a bone is tri- 

 radiate, and it is not always practicable to state which of the three laminte 

 is the free one. In any case the latter is not median on the fixed portion. 

 In the third type of dermal bone, the free keel is much developed and 

 rises into a tuberosity so produced as to be a well-developed spine. The 

 inferior surface of the bone is longitudinally concave. The section of 

 the spine is triangular, the apex being the sharp edge which is the con- 

 tinuation of the keel. The sharpness of this edge is such as to render it 

 probable that these spines constituted dangerous weapons of defense. 

 One side of the spine is nearly vertically over the edge of the base, while 

 the other is within the other edge. The surface of the bone is perfectly 

 smooth. None of the dermal scuta of Belodon described by Von Meyer 

 are developed into spines like those of this species. 



Measurements of dermal hones. 



No. 1. :m. 



-r,. , (anteroposterior 100 



Diameters \ ^ „„. 



( transverse 070 



Elevation of knob 031 



from one end 080 



Distances of knob , „ .i ., , n^« 



from the other end 020 



No. 2. 

 Length 085 



Elevation of laminsii \ ^^ ' 



iNo. 2 016 



No. 3. 



■r,. ^ „ , f anteroposterior 096 



Diameters of base \ , 



transverse 084 



from lateral border 085 



Elevation of spine , - . ^ . 



I. from mferior groove (oblique) 053 



TV. . c • , (anteroposterior 040 



Diameters of spine at base - ' 



( transverse 020 



4. Belodox buceros Cope. American Naturalist, 1881, p. 922. 



Some years ago* I identified certain fossils discovered in North Carolina 

 by Emmons as Belodous ; and later.f referred a species found by Wheat- 

 ley in Pennsylvania to the same genus. I was subsequently able to prove 

 that the genus ranged over the Rocky mountains, and that there, as in 

 other parts of the world, it haunted the shores of the Triassic seas and 

 lakes. There are two species of Belodon in my New Mexican collections, 



* Proceedings of Academy of Natural Sciences, Pliiladelphia, 1866. 

 t Transactions Amer. Philos. Soc, xiv, 1869. 



PROC. AMER. PHILOS. SOC. XXIV. 126. 2b. PRINTED JULY 8, 1887. 



