238 C. D. WALCOTT — I'RE-CAMBRIAN FOSSILIFEllOUS FORMATIONS 



conclusive infonnntion ;is to the extent and character of this remarkable 

 crustacean fauna. 



MEROSTOMA TA 



Genus Beliina, n. g. 



Under this generic name it is proposed to place the fragmentary re- 

 mains of a crustacean, which, as far as can be judged from what we now 

 know of it, is referable to the Merostomata. Thousands of fragments 

 were collected from the calcareous Grej^son shales in both Sawmill and 

 Deep Creek canyons. The test a})pears to have been very thin and with- 

 out an}'- characteristic surface ornamentation; it is usually preserved 

 in strong relief on the drab-colored slate, and its tenuous character is 

 illustrated by figures 2, 3, and 4 of plate 27, which suggest that it was 

 folded and compressed very much like a piece of paper. To one 

 acquainted with the appearance of the test. of Eurypterus and Ptery- 

 gotus as it occurs in the shaly limestones of central and western New 

 York, there would be no question of the resemblance between the frag- 

 ments from those beds and the fragments from the Greyson shales of 

 Montana. In each case the test is very thin and is broken into angular 

 fragments, and often is much distorted and compressed. 



It is probable that more than one genus, and several species, are in- 

 cluded under the genus, but it seems preferable so to include the forms 

 rather than to designate several genera and species on the evidence 

 afforded by the fragmentary material in the collection. Only a few hours 

 were available for collecting material in the field, and it is quite probable 

 that systematic collecting will provide data with which the various forms 

 now placed under Beltina can be classified. 



Plate 25, figure 2, illustrates what may be the head of a Eurypterus- 

 like form, and figure 1 suggests the outline of the head of Pter3^gotus. 

 Tlie telson, figure 18, is the type of that of Pter3"gotus, as is also the 

 free ramus represented b}'' figures 13 and 14, which was undoubtedly at- 

 tached to a chelate appendage. The telson represented b}' figures 4 and 

 5 of plate 26 suggests the telson of Eurypterus or Stylonurus. The 

 fragments represented b}^ figures 2 and 3 of plate 26 and figure 6 of 

 plate 27 suggest jointed swimming appendages, such as occur in man}^ 

 species of the Merostomata. The appendages which have thus far been 

 found vary greatly in appearance, and in the present state of our infor- 

 mation it would be little more than guess-work to attempt to identify 

 them. Sucli forms as are represented by figures 7, 8, and 9 of plate 25 

 suggest the basal joint and a slender terminal joint of the cephalic ap- 

 pendages of Eui'ypterus and Pterygotus. The large appendages indi- 

 cated by figures 6 and 7 of plate 26 suggest the swimming legs, but they 

 are too im]ierfect for identification. 



