. Bulletin - United States National Museum. Science. 94 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. equal and grooved, the distribution of the syzygies is quite different on the pos- terior arms. In the species of Comasteridae possessing grooveless arms it is usually only the two posterior rays which carry them, but in large species with very numerous arms a number may be found on each ray. In Comanthus parvicirra from the Philip- pine Islands Caii^enter found that the distribution of the ungrooved arms, as well as their number, varies to a very great extent. He notes that in any case they alw
. Bulletin - United States National Museum. Science. 94 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. equal and grooved, the distribution of the syzygies is quite different on the pos- terior arms. In the species of Comasteridae possessing grooveless arms it is usually only the two posterior rays which carry them, but in large species with very numerous arms a number may be found on each ray. In Comanthus parvicirra from the Philip- pine Islands Caii^enter found that the distribution of the ungrooved arms, as well as their number, varies to a very great extent. He notes that in any case they always occur on the odd (left) posterior radius, D; Avhen more are developed they may occur on the posterior divisions, Cj and E^ of the two lateral radii, G and E; and when the proportion of nontentaculiferous to tenta- culiferous arms becomes very great, more or fewer of the anterolateral arms Ci and E^ belong to the former class, while in exceptional cases nontentaculiferous arms may even occur on the anterior radii. In only one individual did Cai'penter find a nonten- taculiferous arm on one of the two anterior radii. In this specimen out of 31 arms 19 were entirely devoid of a tentacular apparatus, and in 15 of these the fusion of the two sides of the ambulacral grooves had taken place either on the disk or on the proximal brachials, so that an ambu- lacral nerve was wanting in nearly half of the total num- ber of arms. In the other four nontentaculiferous arms the groove remained open for a short distance and then closed in the usual manner. Three of these four arms constituted the anterior division (E„) of the left lateral ambulacrum, but the fourth was the first arm of the left anterior ambulacrum, and was borne upon the same IIIBr axillary as a well-developed ordinary tentaculiferous arm. In some specimens of Comanthus parvicirra Carpenter found that the arms are all alike in possessing open ambulacral grooves fringed with crescentic lappets and groups of tentacles. In
Size: 1762px × 1418px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorun, bookcentury1800, bookdecade1870, booksubjectscience
