ZOOLOGY. 485 



GranatoblastidcE, with two genera; (5) Codasteridcc, with four genera, 

 two of which belong to tbe special subfamily Phwnoschisjnidce, and the 

 other two to another named Gryptoschismidxc. 



The second order of blastoidea is named Irregulares, and is restricted 

 to "unstalked blastoids, in which one ambulacrum, ami the corre- 

 sponding radial are different from theii fellows," and the " base usually 

 uusj'mmetrical.'' This group includes only one family, long ago called 

 Astrocrifiidw, but amended b}" Messrs. Etheridge and Carpenter, and 

 made to include three genera. 



According to Messrs. Etheridge and Carpenter, the true blastoidsdo 

 not appear previous to the Upper iSilnrian period, and they appear to 

 have become extinct long before the close of the Carboniferous, no traces 

 of blastoids from the Lower Carboniferous (or calciferous sandstone 

 series), much less from any of the marine bands of the coal measures, 

 being recognized. 



All the known blastoids of " the Upper Silurian period are confined 

 to American strata, and represent the families Troostoblastidae and 

 Codasteridse." 



In the Devonian period "all the families are represented. The Si- 

 lurian Troostoblastidae, however, do not appear in the American De- 

 vonian rocks; but they are well represented in Eurojie, although the 

 Devonian blastoids generally are slightly more numerous both in genera 

 and species iu America than in Europe. In Europe the great center of 

 blastoid life in Devonian times appears to have been in the north of 

 Spain, whilst in the British isles there is but the scantiest evidence of 

 their presence in the rocks of that period." (Etheridge and Carpenter, 

 op. cit; An. and Mag. Nat. Hist. (5), xviii, pp. 412-417.) 



Asterioids. 



Organization of star-Jishes. — In the course of investigation of a new 

 incubating star-fish from Cape Horn, to which the name Asferias liyadesi 

 has been given, Prof. Edmond Perrier has described a peculiar organ, 

 and deduced certain conclusions in respect to the taxonomy of the echi- 

 noderms : 



" On the wall of the sacciform canal which surrounds the hydrophoral 

 tube there is attached a problematic organ, which is prolonged beyond 

 the sacciform canal, in such a way as to form two organs (;onnected with 

 the intestine, and giving off two lateral branches, which are in direct 

 relation with the genital glands. This problematic organ, which has 

 lately been called the chromatogenous organ by Hamann, has in young 

 Asterias hyadesi the form of a lateral conical prolongation of the peri- 

 toneal membrane of the digestive sac, and it contains a large number of 

 vitelline bodies identical with those of the wall of the sac. The lobes of 

 its surface are continuous with the trabeculte which form the living basis 

 of the skeleton of the star fish, and it dilates at its external surface into 

 membranes, which envelop the hydrophoral tube. This collateral orgaa 



