300 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



DESCRIPTION OF PLATE 44 



Lingulclla Helena (Walcott) 



Fig. I. (XS-) Exterior of a slightly distorted ventral valve from 

 locality 302s, Middle Cambrian : Park (siliceous) shale, 1.5 

 miles southwest of Helena, Lewis and Clark County. Mon- 

 tana. U. S. National Museum, Catalogue No. 27320a. 



2. (X5-) Cast of the interior of a dorsal valve showing area, 

 from the locality represented by fig. i, U. S. National 

 Museum, Catalogue No. 2732od. 



Figs. I and 2 are the originals of figs. 3 and 3c of Plate 24, 

 Monogr. 51, U. S. Geol. Survey, 1912. 



3 and 4. (X5-) Somewhat distorted dorsal valves associated 

 with typical ventral and dorsal valves such as those repre- 

 sented by figs. I and 2. U. S. National Museum, Catalogue 



Nos. 62545 and 62546. 



The specimens represented by figs. 3 and 4 are from the same 

 shale and locality as those represented by figs, i and 2. 



5. ( X 6.) A small distorted dorsal valve. U. S. National 

 Museum, Catalogue No. 62547. 



The specimen represented by fig. 5 is from locality 4U, Middle 

 Cambrian : Park shale, on the northwest side of Grizzly Gulch 

 about one-half mile southwest of the city of Helena, Montana. 



Obolns ( ll'estonia ) ella ( Hall and Whitfield ) 



Fig. 6. ( X 2.) Impression of the interior of a ventral valve from 

 locality 302s, Middle Cambrian Park shale in Grizzly Gulch, 

 southwest of Helena, Montana. U. S. National Aluseum, 

 Catalogue No. 51686a. Specimen figured by Walcott, fig. \g, 

 Plate 47, Monogr. 51, \J. S. Geol. Survey, 1912. 



7. (X 2,) Slightly compressed and distorted ventral valve. U. S. 



National Museum, Catalogue No. 62548. 



8. ( X 2.) Impression of the interior of a slightly distorted 



dorsal valve from the same locality as specimen repre- 

 sented by fig. 6, showing the characteristic muscular im- 

 pressions. U. S. National Museum, Catalogue No. 51686b. 

 Specimen figured by Walcott, fig. ik, Plate 47, Monogr. 51, 

 U. S. Geol. Survey, 1912. 



