992 
among echini and the form of the test is, in 
each species, unusual. The genus similarly 
named in honor of Lovén is less remarkable, 
but is of interest because it forms one of the 
steps in the progressive differentiation of the 
Paleechinidz. In this series, Lovénechinus 
is intermediate between Maccoya and Oli- 
goporus. Under Melonechinus (this name 
having to replace the more familiar Melon- 
ites, which is preoccupied) particular stress is 
laid on the support which the study of that 
genus with its fourteen species gives to the 
recapitulation theory. The last genus dis- 
cussed, Meekechinus, is a new one and like 
Hyattechinus of special interest, but in this 
case it is the ambulacra which are highly 
specialized, having in each area twenty col- 
umns of plates. The teeth also are remark- 
able in being serrate. Altogether this strik- 
ing Permian genus is a fitting climax to the 
remarkable series of forms beginning in the 
Ordovician with Bothriocidaris. While no 
one will question the right of Hyatt, Lovén 
and Meek to the honor Dr. Jackson has done 
them in connecting their names with these in- 
teresting echini, those of us who are utterly 
opposed to the mixing of honor and sentiment 
with taxonomy must regret that impersonal 
generic names were not preferred. 
In compiling such a systematic monograph 
as is presented in Part III., one invariably 
finds forms so imperfectly described or so in- 
completely known that it is virtually impos- 
sible to determine their relationship to those 
better known. Jackson has very wisely gath- 
ered these unsatisfactorily known forms 
among Paleozoic echini under two heads, 
“Tncerte Sedis” and “Nomina Nuda.” 
Under the former are listed 35 species based 
on single plates, fragments of spines or in- 
complete. and badly preserved tests. Many of 
these can be referred correctly to the family 
and some even to the genus, but, as their real 
relationship to the known forms can not be 
determined, it is a great advantage to have 
them listed in this way and not intercalated 
among the valid species where their dubious 
nature might easily be overlooked. There are 
eleven Nomina Nuda listed, of which Hetero- 
SCIENCE 
[N.S. Vou. XXXV. No. 913 
cidaris keokuk and levispina Hall have a 
curious history, here given by Jackson in full. 
A half a dozen unrecognizable fossils, three of 
which may be Cystoids. are listed under the 
heading “Paleozoic Forms incorrectly re- 
ferred io Echini.” A very full bibliography 
of 248 titles and an equally satisfactory index 
covering 17 pages complete the book. 
A special word is demanded by the illustra- 
tions with which the memoir abounds and 
which are as fine as they are abundant. With 
four unimportant exceptions, every Paleozoic 
species accepted in the text is figured and of 
Many species particularly the more important 
forms, both photographs and drawings are 
used to show the appearance and structure. 
Moreover a large proportion of the figures are 
from the type specimens. The morphology of 
the test and lantern of Recent species is lay- 
ishly illustrated and interesting variants are 
equally well shown. Particular attention 
should be called to the “summary figures,” if 
such a term may be used, showing important 
morphological characters as they appear in 
different groups of echini. Of these, that on 
page 54 illustrating the features of the ambu- 
lacra, the one on page 80 showing the various 
kinds of peristome and that on page 184. which 
gives the different characters of lantern and 
teeth, are of particular importance. but the 
others on pages 70, 134, 148, 193 and 197 are 
really of no less value. 
The chief fault of the book, if one must be 
discovered, would seem to be occasionally un- 
necessary reiteration. This is of course only 
an exaggeration of a virtue due to the author’s 
desire to set forth his facts with perfect clear- 
ness and to marshal them in vigorous sup- 
port of “stages” and the recapitulation 
theory. The same facts or group of facts are 
sometimes repeated in several different places, 
though usually from different points of view. 
This is in part due to the arrangement of the 
book, by which general morphology is dis- 
cussed first and is followed by the application 
to taxonomy and the detailed study of the 
Paleozoic forms. Of course the latter sec- 
tions necessarily contain a large amount of 
morphological detail involving considerable 
