ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 423 
"bile the term joint be restricted to its primitive sense of articulation ; 
that in place of the term joint, as used for a part of an arm, the word 
ossicle or segment should be used. These and other changes which he 
proposes will certainly result in greater clearness, if not in greater 
conciseness. 
Caudina arenata.* — Mr. J. H. Gerould has a memoir on this Holo- 
thurian. After describing its external features and giving an account 
of its habits and food, he enters fully into the details of the anatomy and 
histology of the body-wall, the nervous system, the digestive apparatus 
and the water- vascular system, and the other parts of its organisation. 
His study of the structure of this and allied forms has strengthened in 
1 1 is mind the conviction that the Molpadiidae are more closely related to 
the Cucumariidae than to any other family. This, it is true, has already 
been pointed out by Ludwig. 
Inasmuch as the Synaptidae differ in so many points from other Holo- 
thurians, the idea that they have been derived from a primitive form 
distinct from the ancestors of the remaining families seems not wholly 
improbable. The author, however, is inclined to adopt the view of 
Ludwig, that they represent an early offshoot from the common branch 
of Cucumariidse and Molpadiidae near its junction with the main stem 
from which all Holothurians have arisen. The water-vascular system, 
both in the Molpadiidae and Synaptidae, has undergone a marked de- 
generation, in adaptation to a life of burrowing in the sand. In the 
former, the radial canals and a few rudimentary ambulacra alone remain. 
In the latter, even the radial canals, as Ludwig has shown, are lost 
during the development of the individual. 
Hew Starfishes and Ophiurans.f — Prof. A. E. Yerrill describes a 
number of new species of Starfishes and Ophiurans, and revises certain 
species formerly described. Nearly all these are from the collections 
made by the United States Commission of Fish and Fisheries. In 
dealing with the Starfishes he follows pretty closely the serial arrange- 
ment adopted by Sladen, partly as a matter of convenience, but also 
because it probably represents, in most cases, the real affinities of the 
genera more nearly than any other published classification. In the 
Archasteridae he makes the new subfamilies Benthopectininae and Pon- 
tasterinae ; a new genus Isaster is made for the elegant starfish 
which the author previously described as Archaster bairdii , of which he 
gives a full detailed description. Prof. Yerrill thinks that the families 
Archasteridae, Astropectinidae, and Pentagonasteridae, as described by 
Mr. Sladen, are not well defined, and that the few characters given by 
him do not hold good in all cases. For example, the presence or 
absence of an anal pore, supposed to be characteristic of the first of these 
families, is unreliable ; though whether the pore ever is a true anus is 
very doubtful. The distinctions between the Pentagonasteridae and the 
Archasteridae are also very faint and indefinite, for though the typical 
genera of each group appear to be very different, there are many inter- 
mediate genera now known. It would perhaps be more in accordance 
with a natural classification to drop the family Archasteridae, and dis- 
* Froc. Boston Soc. Nat. Hist., xxvii. (1896) pp. 7-71 (8 pis.). 
f Pruc. U.S. Nat. Mus., xvii. (1895) pp. 245-97. 
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