230 Reviews — Sail ^ Clarke — Paleozoic 8ponges. 



la E V I s ^w s. 



I. — A Memoir on the Paleozoic Keticulate Sponges con- 

 stituting THE Family Dictyospongid^. By James Hall^ 

 State Geologist and Palaeontologist, in collaboration with John 

 M. Clarke, Assistant State Geologist and Palceontologist. 

 Imp. 4to ; pp. 350, plates Ixx and 45 figures in the text, 

 (University of the State of New York, 1898.) 



THIS elaborate monograph treats of a family of siliceous sponges 

 which occur very abundantly in certain portions of the Chemung 

 division of the Upper Devonian in the State of New York ; they are 

 also present in lesser numbers in the sub-Carboniferous rocks of Ohio 

 and Indiana. Beyond the bounds of the United States they are 

 represented by a few forms in the Psammites du Condroz (on tlie 

 same horizon as the Chemung) in the North of France, which have 

 been described by Dr. Charles Barrois ; one species is also known 

 from the Middle Devonian of the Eifel, and another, which appears 

 to be the oldest representative of the family, has been found in the 

 micaceous shales of the Upper Ludlow of Westmorland, and 

 described by McCoy under the name of Tetragonis Dauhiji. 



The sponges of this family are very varied in shape, but the 

 majority are vasiform, cylindrical, or prismatic, whilst others are 

 flattened saucer-shaped, and not infrequently they are of large size. 

 They consist of a thin wall which is built up of fascicles, principally 

 of elongate rod-like spicules intermingled with others of cruciform, 

 five and probably six rays, arranged in vertical and horizontal 

 bands so as to form a lattice-like mesh with rectangular interspaces. 

 With the exception of a few specimens from the sub-Carboniferous 

 rocks of Indiana, these sponges are only known in the form of casts 

 or solid moulds of the interior hollow of the sponge, which has been 

 infilled with the arenaceous or calcareous materials of the rock in 

 which they are imbedded. These moulds retain, very perfectly as 

 a rule, the form of the sponge scarcely at all compressed, and their 

 outer surfaces show, in a fairly definite manner, the impressions 

 of the spicular bands bounding the angular mesh-interspaces. But 

 it is very difficult to determine from the impressions the form, size, 

 and disposition of the individual spicules composing these bands, and 

 hence arises the principal obstacle in the classification of these 

 sponges, which rests to a considerable extent on their outer form 

 and proportions, characters of very subordinate value if Ave may 

 judge from the existing members of the class. 



In some specimens from the sub-Carboniferous rocks of Indiana 

 where the matrix is a calcareous shale or mud, the originally siliceous 

 spicules of the bands are now replaced by pyrites, and it has been 

 possible to determine their forms to a certain extent, but of still 

 greater significance is the discovery in these pyritized specimens 

 of very minute flesh-spicules comparable with those in existing 

 Hexactinellids. Amongst these may be mentioned small regular 

 six-rayed forms with the rays minutely spined, peculiar modification* 



