NO. 12 SPENCE SHALE AND ITS FAUNA RESSER 21 



CLAPPASPIS DOTIS, n. sp. 



Plate 6, figs. 13, 14 



This species is represented l)y the largest number of specimens. 

 It is characterized ])y a short glabella, and closely crowded granula- 

 tions which are of medium size. 



Locality 55c. 



Holofypc and paratypcs. — U.S.N.M. no. 96534. 



FAMILY UNDESIGNATED 



VISTOIA Walcott, 1925 



VISTOIA? MINUTA, n. sp. 



Plate 2, figs. I, 2 



One of the illustrated specimens of this species is mounted as a 

 cranidium, but this may be only an accidental resemblance. Certainly 

 most of the examples available are pygidia. Whenever such trilobites 

 as these retain their full relief, difficulty is experienced in distinguish- 

 ing heads and tails. Consequently, the question is not brought to a 

 final conclusion. 



Even though this trilobite is very small, it is referred to Vistoia 

 chiefly because it fits no other Middle Cambrian genus in any re- 

 spect. It may well be that entire specimens will show that the cra- 

 nidium disagrees with that of Vistoia prisca and then a new genus 

 can be erected. 



Aside from its small size, V. ? minuta is characterized by sim- 

 plicity. The pygidium has a simple, highly arched semicircular out- 

 line. An axis about a third the width of the pygidium is faintly out- 

 lined by shallow dorsal furrows, which do not unite in the rear except 

 by the faintest trace. One specimen retains several simple thoracic 

 segments. 



Localities 55c and 5g. 



Holotype and paratypes. — U.S.N.M. no. 9651 1. 



UTIA Walcott, 1925 

 UTIA CURIO Walcott 



Plate 2, figure 3 



Utia curio Walcott, Smithsonian Misc. Coll., vol. 75, no. 2, p. 60, pi. 14, fig. 4, 

 1924. Idem, no. 3, p. 119, pi. 15, figs. 11-14. 1925- Resser (part), idem, 

 vol. 97, no. 3, p. 9, pi. I, figs. 19, 20, 1938. 



Several hundred specimens of this unique trilobite have now been 

 segregated. One of the cotype cranidia has about nine thoracic seg- 

 ments attached, but no pygidium has been assigned to the species. 



