Review of Recent Geological Literature. 201 
paleozoic crin'^tids as closed; (3) that the distinction which Dr. Carpenter 
considered of the utmost importance as a classificatory criterion— the 
asymmetry imparted by anal structures— is far from being a constant 
character, numerous exceptions occurring among the older as well as the 
recent crinoids; (4) that the various structural features upon which were 
based the great divisions of the crinoids, as presented in part iii of the 
lle^ision, form good distinctive characters ; and Messrs. Wachsmuth and 
Springer propose four great groups into which the Grinoidea may be 
divided, irrespective of age. These well defined primary divisions of the 
Grinoidea are Gamarata; Inadunata, including Larviformia s.nd Fist ulata; 
Artieulata, comprising also the Ichthyocrinid(s ; and GanaMculata, which 
includes most of the mesozoic and recent forms. The paper is illustrated 
by a plate of 21 figures. 
Grotalocrinus: Its Structure and Zoological Position. By Charles 
Wachsmuth and Frank Springer. From Proc. Acad. Nat. Sci., Phila , 
November 27, 1888. Another problematic question has been solved in the 
elucidation of the real structure of a form which has until now been an 
enigma to paleontologists. In the llevision of the Palaeocrinoidea Grota- 
locrinus, together with IcMhyocrinida;, was placed among the Artieulata ; 
but it appears that the basis for such reference was the figures and de- 
scriptions of Angelin, now known to be for the most part erroneous. 
Recently the authors had the opportunity for a critical examination of 
some excellent material from Sweden and England. It was immediately 
noticed that in the construction of the calyx this form resembled closely 
some of the Platycrinidce, and particularly Marsupiocrinus. This fact 
together with various other considerations now places Grotalocrinus, and 
also EnaUocrinus, among the Camarata. One of the most remarkable 
characters of this genus is the peculiar net-like arms. But it is now under- 
stood that the retiary radial appendages are only highly differentiated 
arms, which dichotomize frequently, the branches being connected later- 
ally by small processes projecting from each joint, the whole forming an 
expansion not unlike the fronds of certain Bryozoa. In EnaUocrinus 
which is referred also to the same family, the lateral projections of the 
arm joints are not united, and the arm branches remain free. The 
presence of hydrospires in the Crotalocrinidaj.has not met with the approba- 
tion of Dr. Carpenter, who has denied their existence in this family. 
Messrs. Wachsmuth and Springer, however, have found in the Swedish 
specimens organs apparently of identical structure and similar position as 
the hydrospires in the blastoid genus Orophocrinics. These structures are 
entirely covered by the vault, affording conclusive evidence that they 
could not have been muscle plates, which necessarily should be exposed 
externally. This paper is accompanied by tAvo heliotype plates. Without 
question this method is by far the most satisfactory for the reproduction of 
structural details, but it is quite manifest, that with the plates in question 
sufficient care was not taken with the negatives and consequently some 
of the figures are not quits as distinct as others. 
