Review of Recent Geological Literature, 125 
Nat. Hist, for that year ; a number were published in the Supplement to 
the report on the Geological Survey of Iowa (1860). In each case the orig- 
inal description is reproduced with the addition of such information as 
has since been adduced. This method of treatment makes the work 
very useful to the student. Forty species and varieties are described, 
of which but one, Batocrinus bisbrachiatus (which, though no doubt a 
good species, is bad Latin), is new. 
Ueber silurische Siphoneen ; by E. Stolley. (Neues Jahrb. fur Min 
eral. Jahrg. 1893, II Bnd, 3d Heft. pp. 135-146, pis. vii and viii.) 
The author describes a number of calc-alga? from Silurian boulders 
in the vicinity of Kiel, and suggests the probability that many oolites 
are composed of such organisms. 
Recent studies of the Eurypterina, by Malcolm Laurie. On some 
Eurypterid Remains from the Upper Silurian Rocks of the Pentium I 
Hills. (Trans. Royal Soc, Edinburgh, vol. xxxvu, pt. 1, No. 10. pp. 151- 
161, pis. 1-3, 1892.) The Anatomy and Relations of the EurypteridoB. 
(Idem, pt. 2. No. 21, pp. 509-528, pis. 1, 2, 1893.) Recent Additions to 
our Knowledge of the Eurypterida. (Natural Science, vol.3, No. 18, 
pp. 121-127, 1893.) 
Mr. Laurie brings to the investigation of some obscure points in the 
anatomy of these interesting fossils an evident familiarity with recent 
merostoms and arachnids. The elaboration of the anatomy of 
Eurypteriis and Pterygotus by Schmidt, from the exquisitely preserved 
material from Rootzikull, preceded by the work published by Hall, and 
based upon less favorably preserved specimens from the uppermost Si- 
lurian of New York, and the deductions of Salter, Woodward, Hall and 
Clarke in regard to the composition of Slimonia and Stylonurus, left 
some points in doubt, fewer in the former than in the latter genera. As 
a natural result Mr. Laurie's most important determinations are in re- 
gard to the hitherto less known genera, principally Slimonia, a genus 
not known to be represented in American faunas. In this genus the 
existence of preoral chelate appendages is for the first time established, 
their presence in Stylonurus was shown to be probable by Hall and 
Clarke; in Pterygotus, they have long been known, while in Eurypteriis 
Schmidt made out a pair of preoral filamentous appendages lying be- 
tween the bases of the first pair of walking legs, which have been looked 
upon as tentacular (antennce; see Zittel's "Handbuch"). Laurie, how- 
ever, finds indications that this preoral pair was of a more substantial 
character and probably chelate. The inference is a priori n natural 
one, and if correct establishes a single type of leg structure in 
all these genera. The author's restoration of the ventral surface of 
Slimonia shows five pairs of abdominal plates or sternites, the mem- 
bers of which rapidly diminish in width backward, each bearing on the 
inner surface one or more branchial plates. It seems to be satisfactorily 
demonstrated that sexual differences in this genus are indicated by a 
variation in the form of the genital plate, though similar differences 
have not been established in the related genera. A new generic name, 
