Review of decent Geological Literature. 131 
reached bj the later; that the earlier glaciation was accompanied bj 
mvich the greater submergence, exceeding 400 feet at the mouth of the 
Hudson and extending 500 miles southward, while that of the later 
reached but a tithe of that depth or southing; and that during the long 
interglacial interval the condition of land and sea was much as at present." 
On the Syncanda, a hitherto undescribed synthetic group of Malacostracotis 
Crustacea. By A. S. Packard. (Fifteenth memoir, vol. iii. Proceed- 
ings National Academy of Sciences.) Dr. Packard in this paper discusses 
the taxonomic relations of some interesting fossil Crustacea from the 
Coal-Measure shells of Mazon creek, near Morris, Illinois. The forms 
were first described by Meek and Worthen in the proceedings of the 
Academy of Natural Science, Philadelphia, and were afterwards figured 
and described by the same authors in the geological reports of Illinois, vol. 
iii. The group of Crustacea in question is represented hy the genus 
Acanthotelson. Dr. Packard had placed at his disposal for study a large 
suite of individuals and the results of his investigations lead him to con- 
clude that " the characters of this crustacean are such as to forbid our 
referring it to any known group; we therefore suggest that it forms the 
type of a sub-order of thoracostracous Crustacea, which we would desig- 
nate as the ?>yncaridar 
The presence of a telson and the structure of the last pair of abdominal 
appendages in Acanthotelson indicate relationships with macrouran de- 
capods; but the absence of a carapace, and the division of the thorax into 
distinct, equal segments cavises it to resemble the Edriopthalmia. The 
statement of Packard is that these Crustacea "form a connecting link be- 
tween the Amphipoda and Thoracostraca, but at the same time in their 
most essential characters stand much nearer to the Schizopoda than to 
the Amphipoda." 
It is the same old story. The ancestral forms of our modern fauna and 
flora were synthetic types. 
In the same Memoir as part 11, Dr. Packard treats of The Gampsony- 
chidae an undescribed family of fossil Schizopod Crustacea. The types 
of this family are also from the Coal Measure shells of Mazon Creek, 
Illinois. 
As part III of the same memoir we have a paper by the same author 
on the Anthracaridre, a family of Carboniferous macrourous decapod 
Crustacea. The type of this family is the Anthrapahvmon gracilis of 
Meek and Worthen. Mazon creek is also the locality from which the 
material was obtained. 
The sixteenth memoir, vol. iii, proceedings National Academy of 
Sciences is devoted to a paper by Dr. Packard, on the Carboniferous 
Xiphosurous Fauna of North America. We have here practically a 
monograph of this remarkable group that shows such interesting relation- 
ships with our modern king-crabs on the one hand and with trilobites on 
the other. 
The Carboniferous Xiphostna are divided by the author into three 
families, i, Cychlid^e, represented by Cyclus americanus Packard, 2, Dipel- 
