14 The American Naturalist. [January, 
“Comme aspect chacune de ces marmites avec sa population de 
40 a 60 Echinus, et peut-étre plus, resemble a une façade de 
maison avec un habitant a chaque fenétre ouverte et qui seraient 
occupés a regarder ce qui se passe. Tous les échinides étaient 
bien portants, et je n’en ai pas vu de mort. 
“JuLEs Marcov.” 
According to Fisher, Cailliaud says that excavations by sea- 
urchins were observed at Biarritz by MM. Szmann and Cazena- 
vette. This was probably the first observation of this habit in 
this locality, but I am unable to discover from Cailliaud’s account 
that the peculiar relation to pot-holes was noticed by them, or 
by any author quoted by him in the preparation of his paper. 
It is remarkable that such an interesting case of erosion should 
have escaped their observation, a fact which may be ascribed pos- 
sibly to the inaccessible position in which these rock erosions 
were to be found. Marcou was engaged in collecting fossils 
when the pot-holes were discovered, which led him to portions of 
the coast not easily visited.” 
Fisher also observed that the common sea-urchin at Biarritz 
has the habit of excavating, although the relation of these ur- 
chins to pot-holes in that locality seems to have escaped his 
notice. He writes: “A marée basse une grande partie des 
rochers du Port-Vieux sont émergés et rejoinnent quelques blocs 
plus élevés, placés au large, qu'il serait facile de relier par une jetée. 
La mer bat vigoureusement contre des roches plus résistantes 
que les falaises de la côte des Basques; le sol du port est un 
sable trés-fin. . . . Quand on examine les rochers 4 marée 
basse, on trouve au-dessous de la ligne d’émergence des excava- 
tion sprofondes, de grandeur variable, depassant quelquefois un 
mètre carré en superficie. Jamais ces excavations ne manquent 
d'eau, lors même que leur contour émerge a l’epoque des grandes 
marées; leur profondeur permet á la mer d’y laisser au moins un 
% At the time of his visit Prof. Marcou was not specially engaged in a study of the 
work of these animals, but the examples of rock erosion were so striking that his atten- 
ion was attracted to them, and he retains to-day thirteen years after his visit, a vivid 
memory of them. On his return to America he called the attention of several persons to 
his observation, but nothing was published, and apparently no great interest was excited 
them. 
$ 
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