Review of Recent Geological Literature. 125 
Let who will make these, here are the facts, says the preface and 
nothing is clearer throughout the contents of the book than that its 
writer is dealing precisely and cautiously with facts alone. Either the 
author has not, or believes he has not, found the key to nature's method 
of jjroducing lamellibranchs. Some critics might say that here is a fine 
opportunity missed for excursions in these fields. 
So significant are the results of this work to the large numl)er of stu- 
dents of paleozoic faunas that a somewhat extended notice of them is 
justified. The paleontological part opens with the systematic descrip- 
tion of species and genera. 
Family Mytilida?. Modiola Lamarck. The author considers the De- 
vonian existence of this genus as proven, two described species posses- 
sing not only the typical form but also a small anterior adductor close 
beneath the beak, a curved, narrow, uuthickened, toothless binge and 
a linear marginal groove. It is possible that some of the American 
shells now referred to Modiomorjiha will jjrove congeneric with these. 
Family Modiolopsidaj. Modiomorpha Hall. The hinge structure of 
this genus is more fully elaborated than was done by Hall. The latter 
made out a single tooth in the left valve and a cerresponding socket in 
the right valve. It is found that the left valve may have a tooth on 
either side of the median socket, one or Vjoth being absent on some spe- 
cies. Hall also made out the ligamental groove as external, but this is 
here stated to be a flattened surface so strongly striated as to suggest 
lateral teeth. 
Nyassu, Hall. Though nothing new is added to the generic structure, 
the type species N. arynta, the common form of the genus from the 
Hamilton group of New York, is regarded a synonym for Sangainolaria 
(N.) dornata Goldfuss. To us, however, the specific difference seems 
well defined. 
Dolahra, McCoy. This genus, referred with doubt to the aviculoids, 
still remains imperfectly known, no clue to the hinge structure being 
yet obtained. 
Family Arcidae. Macrodus, Lycett., (emended spelling]. Without 
adding any new structural details, attention is called to the variation in 
size of the triangular ligament area, which is small in all these middle 
Devonian sjjecies but often becomes of greater extent in Carboniferous 
forms of the genus. 
Family Nuculidfe. Nii.cula, Lamarck. Fifteen species of small, sub- 
triangular, characteristically Devonian shells are described, and it is 
shown that Neumayr's genus Mijoj)li(nia, introduced for some of Bar- 
rande's "Nuculas" and based upon the presence of accessory muscular 
scars, is not to be distinguished in this respect from either Nucula or 
Cienodonta. 
Nnculana, Link. This name is preferred to the term Leda, Schum., 
more commonly employed but said to be preoccupied. The 7 species 
described show the arcoid teeth, median ligamental groove as in Nu- 
cula, the pallial sinus and the contracted outline peculiar to the genus. 
