INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 447 



unobserved arrangement ; to make this clear, it will be necessary to 

 state what obtains in the allied forms. In the Ophiurida the mouth- 

 parts are more metamorphosed than they are in the Asterida ; in the 

 latter, the first two suckers arise independently of one another from 

 the radial water-vessel, but in the Oj)hiurida they have a common 

 canal, and this, as well as its two branches, lies in the calcareous pieces 

 of the peristome, but the water-vascular ring is not enclosed in these 

 pieces. Now, in Astrophi/foii a part of the ring is so enclosed, and we 

 have, therefore, in it (and perhaps in all other Euryalida) a further 

 metamorphosis of the constituent parts of the peristome than we find 

 iu the Ophiurida and, a fortiori, than in the Asterida. 



In conclusion, the author discusses the homology of the buccal 

 shields of the Ophiurida, and finds that they ai'e homologous with the 

 oral plates of the Crinoids, and the genital plates of the Echinoidea. 

 Herein he so far agrees with Mr. Philip Carpenter that he thinks to 

 be certain what the English observer thinks to be possible — namely, 

 that the oral shields of the Ophiuiida are homologous with the oral 

 plates of the Criuoidea. 



Undescribed Comatulse from the British Secondary Rocks.* — 

 Ml". P. II. Carpenter describes seven new Comatulse from the creta- 

 ceous and oolitic scries of southern England, together with some 

 new facts respecting the Glenotrenites paradoxus of Goldfuss, from the 

 upper chalk. This species is remarkable for the presence of certain 

 characters which are very cons2)icuous in the recent Antedon Esch- 

 richtii, and also in a new sjjccies dredged by the ' Challenger ' at 

 Heard Island iu tlie South Atlantic, namely, the presence of strong 

 ribs on the inner wall of the centrodorsal, five of which, interradial 

 in position, are much more prominent than the rest. So far as is yet 

 known, these features occur in no other recent Comatula, with the 

 exception of one species from the South Pacific, in which there is a 

 faint indication of such ribs ; but they are all equal. Another 

 Autcdun species is described from the chalk of Sussex. It difi'ers 

 from Autcdou paradoxus in the absence of these ribs, and in the 

 shallowness of the centrodorsal cavity. 



Two sjiccies are described from the gault of Folkestone. One is 

 an AniedoH with no special relations to any recent forms. It might 

 have lived as well at twenty as at five hundred fathoms. But the 

 other species is an Actinomctra, possessing certain characters only 

 known to occur in si)ecies from quite shallow water, twenty fathoms 

 or less, in the Philippine Islands and Malay Archipelago. Tlie 

 centrodorsal is a flat plate, nearly on a level with the surface of the 

 radials, or sometimes even below them, sci)arated from tliem by clefts 

 at its sides, and entirely devoid, not only of cirrhi, but also of cii'rhus- 

 Bockets. This condition is only an extreme stage of the metamor- 

 phosis of the centrodorsal piece, which b(;ars cirrhi for a time after 

 its liberation frcnn the larval stem ; but these cirrlii eventually dis- 

 appear, und tluiir sockets become obliterated. The ' Challenger ' 

 collection contains a series of spocimeus of Act. Jukesii from the 



* ' Quart. Jouru. Gtul. Soc.,' xxxvi. (1880) p. 3(j. (1 jilatc.) 



