BRACHIOPODA. 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. Grunti. 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 Lingulops."f [PL xiii, fig. 2.] 



Shortly after the first publication of this notice, in March, 1871, gutta-percha 

 impressions, taken from the single internal cast of I/. 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 Trimerellid9e.§ The 

 minuteness of these fossils requires the greatest care in the determination of 

 their internal markings, and the diversity of opinion which 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. 9a) 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 papei-." 

 § Quart. Journ. Geol. Soc, vol. xxx, p. 164. 1874. 



