BRA CHIOP ODA. 
19 
or reddish sandy shale found on the Maquoketa creek, twelve miles north¬ 
west of Dubuque, Iowa, and the Lingula Norwoodi, of the late U. P. James, 
from southern Ohio and northern Kentucky; both being from rocks now 
referred to the age of the Hudson group. The third species is one here 
described* * * § from the Niagara limestone at Hamilton, Ontario, L. Granti. All the 
shells are of small size, rarely exceeding 6 mm. in length, and all have 
essentially the same external aspect, but the internal casts, often retaining the 
character of the muscular markings in exquisite detail, show important 
peculiarities for each species. Of the original species, L. Whitfieldi, very few 
specimens have been obtained. In the first notice of the genusf the diagnosis 
given was very brief, and in the following terms: 
“ The ventral (?) valve presents a small area with a narrow pedicel groove, 
and a large lobed muscular impression, which in the cast extends as a narrow 
groove towards the base of the shell. The character of the area and foramen 
differ from the typical forms of Lingulella, though in that genus the form and 
character of the muscular impression has not been determined, so far as I am 
aware. For this shell I propose the name LingulopsAX [PI. xiii, fig. 2.] 
Shortly after the first publication of this notice, in March, 1871, gutta-percha 
impressions, taken from the single internal cast of L. Whitfieldi, which had served 
the purpose of the original illustration of the genus, were sent by his request, to 
Mr. Davidson, and upon these was based the analysis of Lingulops given by 
Davidson and King, in the appendix to their paper on the Trimerellidae.§ The 
minuteness of these fossils requires the greatest care in the determination of 
their internal markings, and the diversity of opinion ^hich has already been 
expressed, both in words and illustration, in regard to these features in the 
type-species, must be, to an important degree, due, to the personal equation in 
observation. Upon plate xix, accompanying the paper of Messrs. Davidson 
and King, a lithographic figure (fig. 9 a) is given of the single interior then 
known, agreeing, except in some minor details, with the original illustra- 
* See Supplement. 
t Imperfectly known Forms among the Brachiopoda, etc. 1871. 
I “ Printed Ligulops by mistake in some copies of the paper.” 
§ Quart. Journ. Geol. Soc., vol. xxx, p. 164. 1874. 
