OCR Text |
Show 740 MR. P. H. CARPENTER ON THE [DeC 19, absence of palmars or of any further ray-divisions. One finds the same deficiency of information in the formulae for the following species, viz. Antedon bimaculata, brevicuneata, elongata, flagellata, lavicirra, macronema, palmata, regince, spinifera. Had I not examined eight of these personally, I should be unable to classify them properly from Prof. Bell's formulas alone. The remaining one (Ant. regina) is an M S . species of his; and I am therefore unable to give it a place in the classified list of species which concludes this paper. The only irregular types to which Prof. Bell's notation is at all applicable are those like Act. rotalaria, which have two distichals and three palmars, with a syzygy in the last axillary but not in tbe distichal one. He gives the formula of this species as 3A'(P)^; but this tells us nothing as to the number of the distichal joints; and Prof. Bell is unable to carry out his plan of inserting the sign V to indicate that the distichal axillary is not a syzygy, because it would not apply to the palmars. A specialist would know that there are only two forms of distichal series yet described in Actino-metra, viz. two joints, the axillary without, and three joints, the axillary with a syzygy; so that the omission of D from Prof. Bell's formula would lead him to infer that only two distichal joints were present in the corresponding species. But Prof. Bell gives no hint of this fact for the benefit of the uninstructed collector ; and should an Actinometra ever be discovered with four distichals and three palmars (the last axillary a syzygy), instead of two palmars without a syzygy (as is actually the case in one species), it would have the same formula as Act. rotalaria, though widely different from it in reality1. When, however, the case of Act. rotalaria is reversed, and there are three distichals and two palmars, the distichal axillary having a syzygy and the palmar not, Prof. Bell's notation is altogether insufficient. He cannot insert a P, because there is no syzygy in the palmar axillary; and he cannot use the sign s/, because there is a syzygy in the distichal axillary. He is therefore obliged to content himself with making no mention of any palmars at all. Omitting the cirrus-characters, we find his formulas for the six following species to be all of the same general type, viz. 3 A (or A') D. The species are-Antedon briareus, A. decipiens, A. irregularis, and A. savignii, Actinometra trichoptera and A. multiflda. All of them have three distichals with the axillary a syzygy ; but some of them, Ant. savignii and Act. multiflda, also have two palmars, while others, like Act. trichoptera, have not. Prof. Bell, however, gives the same group-formula in each case, so that I am unable to refer his two species, Ant. decipiens and Ant. briareus, to their proper positions; and I have only been able to place Ant. irregularis in m y classified list, owing to his having kindly permitted me to examine it for myself. Both Ant. decipiens (3AD^\ and Ant. 1 I am here speaking only of the ray-divisions, and take no account of the characters of the cirri, which might or might not be different in the two species. |