ICC DEVONIAN FAUNA. 



Front margin gently convex. Valve with a median depression. Surface 

 covered with about twenty strong, distant, alternating ribs, whicli have the appear- 

 ance of being microscopically lineated and granulated. 



Size. — Height 4 mm., width 5 mm. 



Localities. — Two or three specimens are on a slab from Saunton in Miss 

 Partridge's Collection, and its reverse in the Porter Collection. I have, I believe, 

 observed two or three better specimens of this tiny shell, but, failing to take note 

 of them at the time, am now unable to find them. 



Remarks. — Phillips figured a specimen which is almost identical with ours, both 

 in size, shape, and ornament. This he referred to 0. interlineata, but it seems to 

 me questionable if our shell be the young of that species, as it seems distin- 

 guished not only by the fewness of its ribs, but by the size of its umbo and 

 by several other points. We have not, however, sufficient evidence to enable us 

 to arrive at its true character. 



2. Genus — Orthotetus, 1 Fischer de Waldheim, 1830. 



1. Orthotetes crenistria (Pliillips), var. arachnoidea, Pliillij>s. Plate XX, figs. 



10, 11. 



1836. Spirifer aeachnoideus, Phillips. Geol. Yorks., vol. ii, p. 220, pi. xi, 



fig. 4. 

 ? 1841. Oethis semicibculaeis, Phillips. Pal. Foss., p. Go, pi. lviii, fig. 112*. 

 1865. Steeptobhtnchus crenistria et var. aeachnoideus, Davidson. Brit. 



Foss. Brach., vol. iii, pt. 5, p. 81, pi. 

 xviii, figs. 4, 7. 

 1896. Orthotetes crenistria, Whidborne. Proc. Geol. Assoc, vol. xiv, p. 376. 



1 I have to thank Professor liupert Jones for the trouble he has taken in deciding the ortho- 

 graphy of this name. It was originated in 1829 by Fischer de Waldheim (not by Evans) ('Bull. Imp. 

 Soc. Nat. Moscou,' p. 375) for a shell found by Mr. Evans at Pakhrino, which he {i. e. Fischer) 

 believed to be of a new genus, and named Orthotetes, deriving it from dp0wr//$ (*'. e. 6p66rr)s), " straight- 

 ness," because " at the hinge is a transverse impression straight and linear." In 1837 (' Oryct. Gouv. 

 Moscou,' p. 133) he repeats the same spelling and derivation, and figures the shell. In 1850 ('Bull. 

 Imp. Soc. Nat. Moscou,' p. 491) he describes and figures it under the same name, and distinguishes it 

 from Orthis. 



Professor Bupert Jones writes, " Orthotetes was made wilfully from op0wr>/s, and, though irre- 

 gular, must be accepted as an intended name." Bronn and Davidson wrote it thus ; but later authors, 

 e.g. Zittel, (Ehlert (deriving it from opdos), and Hall, changed it to Orthothetes. Orthothetes might be 

 derived from 6p8u$ and dirrji, but that would mean " the adoptive father of straight things " (or ? of an 

 Orthis), and would be (even on evolutionary principles) hardly an improvement on Fischer's original 

 malformed word. If altered at all it should have been changed to Orthotes. 



