NO. 1985. NEW SPECIES OF SILURIAN FOSSILS— WILLIA2IS. 341 



Davidson, however, recognized the distinctness of the two species 

 and redefined L. minima as follows: 



Shell small, oblong, elongated; sides curved, gradually merging into the slopes 

 forming the acuminate pointed beaks; front rounded; valves slightly convex and 

 marked with fine concentric striae. Two specimens measured 4 by 2J and 5 by 2^ 

 lines (the latter a Lesmahago specimen). 



And on his plate 2 the difference between the two species becomes 

 clearly manifest.^ 



Adopting Davidson's interpretation of the species L. minima, I can 

 find little other than varietal modification to separate our Pembroke 

 Lingulas from L. minima. Our shell is a little more slender than the 

 Davidson figures average. 



The specimens figured by Davidson from Lesmahago called L. 

 unguiculus Salter MS, approach more nearly the general characters 

 of the American variety than do those from the Downton sandstone, 

 old Leominster Road near Ludlow, which is probably closer to the 

 type as defined by Sowerby. In case our variety were to be regarded 

 as of specific rank separate from X. minima, the name L. unguiculus 

 Salter may be substituted. * 



The specimen I have figured is a fair average specitnen; other 

 specimens from the same purple shales differ in size, some larger and 

 some smaller. They are all characterized by the elements of form 

 described in the definition, and the larger number of specimens ob- 

 served in the formation are smaller than the specimen figured. They 

 differ from L. cornea, as figured and described (and as represented in 

 the Eastport Lingulas) in the more curved side and front, the more 

 acute beak, and the slightly greater length in proportion to width. 

 The size, is, however, a diagnostic character. In the Pembroke 

 formation Lingulas of the cornea type appear, but they are rarely 

 seen in the Hersey red shale member, where the characteristic Lin- 

 gula is the small one. 



Formation and locality. — Pembroke formation, the upper red shales 

 (Hersey member) on the shore of west side Sipp's Bay south of high- 

 way bridge, Pembroke Qoc. No. 2.32.9A). 



Holofype.— Cat. No. 58973, U.S.N.M. 



Comments. — The figure given of this variety (pi. 31, fig. 6) repre- 

 sents a selected specimen of the average form and size (the figure is 

 drawn twice the size of the original) of the Lingulas met with fre- 

 quently ia both the gray and the purple shales of the Pembroke for- 

 mation. It is easily distinguished from the wider and larger species 

 from the higher (Eastport) formation, which I have identified with 

 Lingula cornea Sowerby. Specimens of a more slender and also of a 

 wider form are represented in the collection. The variable form is 



1 Brit. Sil. Brach., p. 48, pi. 2, figs. 36-44. 



