A MONOGRAPH OF THE EXISTING CRINOIDS 567 



Siboga Exped., 1918, p. 98 (in key; range), p. 107 (key to the included species). GISL^N, 

 Zool. Bidrag Uppsala, vol. 9, 1924, p. 84 (syzygies), p. 230 (disk), p. 235. 



Diagnosis.- A genus of Mariametridae in which the lateral portions of the division 

 series are ornamented with more or less closely crowded small tubercles or spinules; 

 P 3 is the longest and largest pinnule, usually markedly longer than P 2 or P 4 , though 

 sometimes not greatly longer (and in young or undeveloped individuals or on un- 

 developed arms occasionally shorter), and tapers gradually to a delicate tip; the 

 division series are usually in close lateral apposition with more or less flattened sides, 

 less commonly just in contact or even free laterally with the sides slightly or even not 

 at all flattened ; the cirri are of moderate length, with 24-40 segments, of which the 

 outer are simply carinate dorsally or bear more or less strongly developed dorsal 

 spines or tubercles. 



Geographical range. Southern Japan from the Oki Islands in the Sea of Japan 

 to Tokyo Bay and southward to Amboina, the Kei Islands, Timor, Flores, and Sapeh 

 Strait, between Sumbava and Komodo, and westward to the Mergui Archipelago. 



Bathymetrical range. From 40 to 153 meters. 



Remarks.- -As understood herein the genus Mariametra includes five species, 

 three of which, delicatissima, tuberculata, and tenuipes, are known from only a single 

 specimen each. The two best-known species, subcarinata and vicaria, seem to be 

 very distinct, but the relationships of the other three are more or less obscure. 



Except for the occurrence of spinous or tubercular ornamentation along the sides 

 of the division series, which is a more or less trivial feature, and the greater slenderness 

 correlated with the smaller size, there are no tangible differences between the species 

 of Dichrometra and those assigned to the genus Mariametra. The species of Maria- 

 metra are simply rather small species of the Dichrometra type inhabiting in general 

 rather deeper water than the species of Dichrometra. While the species of Dichrometra 

 are mainly littoral, the species of Mariametra do not approach within 40 meters of 

 the surface; but, on the other hand, the greatest depth at which a species of Mariametra 

 (delicatissima) has been found is 153 meters, though a species of Dichrometra (afra) 

 is known from 164 meters. 



History. The genus Mariametra, with the genotype Himerometra subcarinata 

 A. H. Clark, 1908, was established by me in a paper on new recent Indian crinoids 

 published in 1909 in the following terms: 



The form which I described under the name of Himerometra subcarinata differs markedly from 

 all the other species in the genus Dichrometra, where I had tentatively placed it, in having a delicate 

 narrow carinate line in the middle of the dorsal surface of the division series and first two brachials, 

 and in having the sides of the division series thickly covered with fine granulations forming a trian- 

 gular figure in each interradial area, with the apex at about the level of the last axillary, something 

 similar to the ornamentation found in certain species of Crinometra. There are also differences in 

 the cirri and in the pinnules, and the surface of the disk adjacent to the ambulacra is strongly plated. 

 It did not seem wise to create a genus for this single aberrant species, as it was then impossible to 

 judge of the value of the characters exhibited, they not being met with in any other species of the 

 Himerometridae. The Indian collection, however, contains another species possessing the same 

 general features which separate subcarinata from the remaining species of Dichrometra, though 

 differing widely in its details, and I have now no hesitation in creating a genus for these two peculiar 

 forms, which I propose to call Mariametra. 



