Nov. 10, 1881] 
NATURE 
41 
after a wide défowr re-crosses east of Hermann, returning 
to the south-west, thus forming an immense cape-like 
area of maximum declination to the east of Jefferson 
City. It is therefore improper to regard the chart re- 
ferred to as more than a representation of observations 
_then made, although the stations were more numerous 
than is usually deemed necessary for an area of 60,000 
square miles. 
The area of minimum declination represented on the 
chart of April 21 has been more satisfactorily outlined, 
and aclosed area of maximum declination lying to the 
west has been determined with certainty. 
The work of the past summer has therefore increased 
the complexity of the isogonic lines, and the gradual 
change in declination in passing through these areas of 
abnormal value shows that the causes must act over 
areas of from I000 to 3000 square miles, z.e. that the 
observed effect is not due to minute local causes at the 
several stations. It will not be possible to determine 
fully the extent of these abnormal influences until similar 
work done in adjoining States shall enable a more precise 
determination of zozmal values. The stations of obser- 
vation in Missouri now number over 100. Arrangements 
for the summer of 1882 have already been made, and the 
survey will be carried forward on a still more extended 
scale. FRANCIS E, NIPHER 
St. Louis, October 8 
THE ECHINOIDS OF THE “CHALLENGER” 
OOLOGISTS in general, and echinologists in par- 
ticular, will welcome vol. iii. part 9 of the “ Report 
on the Scientific Results of the Voyage of H.M.S. Chal- 
lenger,’ which has just been published. It deals with 
the Echinoidea, and has been prepared by Prof. A. 
Agassiz, a more competent reporter than whom it would 
be difficult, if not impossible, to find. We do not propose 
to do more than give a brief outline of the principal results 
brought to light in this portly volume, which runs over 
some three hundred pages of text, and is illustrated by 
sixty-five plates. 
Commencing with a few remarks on classification, 
Prof. Agassiz ; asses on to treat at more length of that 
vexed question of the position of the axis of the Echinoidea. 
He dissents from the theory put forward by Lovén in 
his “ Etudes,’’? a memoir which, however much one may 
differ from it, cannot be read without a feeling of admira- 
tion of the “infinite skill”—to quote Prof. Agassiz’s 
happy expression—-displayed by the author. Our reporter 
again asserts the position he has al! along held, that, 
judging from embryological data, the position of the axis 
is in the main determined by that of the madreporiform 
plate. Next in order he deals with the structure of the 
coronal plates, the anal system, the fascioles, and the 
structure of the spines. In connection with the latter 
subject Prof. Agassiz takes exception to some views which 
we have elsewhere put forward as to the systematic value 
of acanthological characters. His opinions on any point 
of-Echinoid structure merit the highest respect, and so we 
do not propose to enter here into an examination of his 
criticism on our work—a criticism, be it said, which is 
conceived in the true scientific spirit. A more fitting 
opportunity will offer itself in a further communication on 
the subject with which we are at present engaged. The 
reporter then goes on to notice with extreme aversion the 
attempts to construct “ genealogical trees” “ which have 
become so fashionable.” In spite of Prof. Agassiz’s well- 
earned reputation, however, one reads with a sort of 
shudder the assertion that he is about “to show once for 
all how futile it must be to carry on’’ these attempts, 
especially when we remember the men of mark who 
engage in them. But a genealogical tree is a upas tree 
to Prof. Agassiz, and he attacks it with hearty good will, 
albeit we think that the mathematical axe which he wields 
is by no means so destructive as he appears to believe. 
That relations exist between the different groups of 
Echini no one knows better than Prof. Agassiz, and in 
the next two or three sections of his Report he shows 
how well he can use his knowledge in the interesting con- 
nections he traces between recent and fossil Urchins, 
and since this relation does exist we cannot see why the 
attempt to indicate it graphically or descriptively is to be 
condemned as futile, even though there may be a minimum 
of 2” possible combinations of variables. Having passed 
in review the relations between recent and fossil Echinoids 
the reporter then comes to what is the real sum and centre 
of his Report, the description of the species and genera, 
and here we have an abundance of most interesting 
matter. 
The Challenger Expedition has added fifty-two new 
species, comprised in fifteen new genera, to our list of 
Echinoids, a very considerable addition when we remem- 
ber that the order is a comparatively small one. The 
group which has been most largely increased is that of 
the Echinothuridz, of which twelve new species have 
been described, whilst of the Echinometridz, Clypea- 
stride, and Spatangina only previously known forms have 
been obtained. It would be of course out of the question 
to notice all the interesting facts brought to light here; 
the Report itself must be read for this, and we are fain 
to content ourselves with a few passing remarks‘on some 
of the more striking forms. The remarkable genus 
Asthenosoma, which was established by Grube in 1867 
(Calveria, Wyville Thomson, 1869) to contain an Urchin 
with a flexible test has been increased by the addition of 
five new species with a very varied bathymetrical range, 
one having been obtained at 10 fathoms and another at 
1400. _Wyville Thomson’s genus, Phormosoma (1874), 
has afforded seven new and most interesting species, in- 
habiting, as a rule, deeper water than its companion 
genus (255 fathoms to 2600 fathoms). To this genus 
belongs the honour of furnishing the largest Urchin which 
Prof. Agassiz has hitherto met with, P%. hoplacantha, 
Wy. Thoms., measuring 312 mm. in diameter—truly a 
good-sized specimen. Amongst the Didematidze we have 
a remarkable new genus, Aspedodiadema, with the abac- 
tinal system and ambulacral plates of a Cidarid combined 
with the thin test and hollow spines of a Diadema. 
Micropyga is another hitherto undescribed genus of the 
same family. Passing over the Echinometride (no new 
species), the Temnopleuridz (three new species), the 
Triplechinidz (one new species), and the Clypeastridz 
(no new species), we notice amongst the Petalosticha 
thirteen new species of the curious genus Pourtalesia (A. 
Agass., 1869) with its remarkable beaked test; and, 
amongst other new genera, Cystechinus, which appears 
to be related to the fossil genera Galerites and Anan- 
chytes. We might go on for a long time noting one 
interesting form after another, were it not that to do so 
would make this notice inordinately long. How far 
further study and discovery will affect the number of 
genera and species enumerated here it is impossible to 
say, but as Prof. Agassiz is by no means given to multi- 
plying species, and as most of the specimens appear to 
have been well preserved—only a few having been de- 
scribed from fragments—it is likely that the greater num- 
ber will stand. A word in conclusion as to the plates, 
The majority of them have been drawn by Mr. Roetter, 
and we congratulate Prof. Agassiz on having at his 
disposal the services of so gifted a draughtsman. Many 
of the plates are to our mind very gems of lithographic 
art. The drawings of the sections of spines, though 
very pretty, and in most instances handled with great 
delicacy and finish, do not always give the clearness of 
detail that could be desired, and the mechanical arrange- 
ment both of these plates and of those containing the 
pedicellariz and the side views of spines is decidedly 
objectionable. It may be that Prof. Agassiz and his 
