330 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.38. 



to examine sonic hundreds of Antedons representing all the localities 

 inhabited by the genus, and I find thai there are four perfectly dis- 

 tinct and readily recognizable species, two inhabiting the Atlantic 

 coasts of Europe and two the southern shores cast of the Straits of 

 Gibraltar. For the two first the names Alecto petasus Duben and 

 Koren, 1846, and Asterias bifida Pennant, 1777, are available, while 

 one of the two last should bear the title of (Comatula) mediterranea 

 Lamarck. L816. The fourth species, which so long ago as 1792 Olivi 

 found to be abundanl in the Adriatic Sea, has never been recognized 

 by systematists, but has always been considered the same as the 

 preceding, which, in turn, has usually been confused with the bifida 

 of Pennant and often, in addition, with the petasus of Diiben and 



Koren. 



These four species, far from being so closely related that only an 

 extremist can distinguish them, may be at once recognized at sight 

 by anyone who will take the trouble to make himself familiar with 

 their characters; the two Mediterranean forms have very long and 

 slender arms, and long slender cirri with numerous segments, while 

 the Atlantic species have much shorter and stouter arms and cirri, 

 the latter with fewer segments. Antedon petasus differs from A. 

 bifida chiefly and most obviously in the very much greater number 

 of its cirri, while the two Mediterranean forms are most readily differ- 

 entiated by the proportionate length of the cirri and by the numbers 

 of their component segments. 



A review of t he facts presented by the study of comatulicl ontogeny 

 shows that Antedon bifida, and especially A. petasus, represent a 

 phylogenetically more advanced condition than the comparatively 

 primitive Mediterranean forms, and that of these latter the Adriatic 

 species is less developed than the one found from Italy westward. 

 Now the Adriatic form usually has four or five underbasals, and the 

 one occurring at Naples, Toulon, and Villafranca three. No under- 

 basals have ever been found in Antedon bifida, but this is not at all 

 remarkable, nor does it reflect upon the powers of observation of the 

 able naturalists who have studied it; for if the comparatively slight 

 specialization of Antedon mediterranea over the Adriatic species is 

 sufficient to result in the reduction of the number of underbasals 

 from tour or five tot hree, we may readily infer t hat the much greater 

 degree of specialization of .1. bifida over .1. mediterranea would result 

 in the elimination of underbasals entirely from the ontogeny of the 

 former. 1 can -«•.• no reason whatever for doubting the accuracy of 

 the work of Wyville Thomson, Perrier, and the two Carpenters, who, 

 none of them, found underbasals in Aii/<</<m bifida, and I should be 

 greatly surprised if anyone in the future should find them in that 

 species or in .1. petasus, except, perhaps, in sporadic instance-. 



