296 bulletin: museum of comparative zoology. 



The following list gives these names with the name of which each is a 

 synonym: — 



atacamensis (Philippi) = kroyeri Liitken 



brachygenys H. L. Clark = plana Lyman 



brocki de Loriol = savignyi Miiller and Troschel 



corallicola Koehler = abyssicola (Sars) 



cuspidata Lyman = abyssicola (Sars) 



dispar Verrill = miilleri Liitken 



echinata Koehler = abyssicola (Sars) 



flexuosa Lyman = plana Lyman 



fragilis Ljungman = kroyeri Liitken 



incisa von Martens = savignyi (Miiller and Troschel) 



krebsii Liitken = savignyi (Miiller and Troschel) 



Ijungmani Marktanner-Turneretscher = miilleri Liitken 



longibrachia H. L. Clark = miilleri Liitken 



magellanica Ljungman = asperula (Philippi) 



orstedii Liitken = simplex (Leconte) 



perplexa Koehler = plana Lyman 



poa Lyman = abyssicola (Sars) 



profundi Liitken and Mortensen = plana Lyman 



reinhardtii Liitken = savignyi (Miiller and Troschel) 



sexradia (Grube) = savignyi (Miiller and Troschel) 



virescens Liitken = savignyi (Miiller and Troschel) 



To the remaining 35 species of Ophiactis I have been obliged to add 

 one, of which numerous examples were collected in Buccoo Bay, 

 Tobago. These 36 species, which appear to be valid, form a 

 rather homogeneous group within which specific lines are not often 

 very clearly drawn. Adult specimens, as a rule, have well-marked 

 characters, but young individuals are frequently very perplexing, and 

 young specimens are much more generally collected than adults. The 

 genus falls rather naturally into two sections according to either one 

 of two characters, the shape of the upper arm-plates and the number 

 of oral papillae on each side of the jaw. The upper arm-plates are 

 either more or less fan-shaped or they are transversely ellipsoidal or 

 tetragonal ; in the former case, they are little or not at all in contact,. 

 in the latter, the line of contact nearly or quite equals the width of 

 the arm. But the upper arm-plates in all very young specimens are 

 triangular, becoming fan-shaped, and this condition is of course present 

 at the tip of the arm in all members of the genus. When, therefore. 



