330 BULLETIN lOO, UNITED STATES NATIONAL MUSEUM. 



The chief differences between the young and medium sized speci- 

 mens (as No. 4) are to be found in the extremely thin membrane 

 and few or no granules of the former. A very young eristatus does 

 not appear to belong to the same genus as the adult. In specimen 

 No. 1, for example, the outlines of the abactinal plates are clearly 

 visible and the thin membrane might be described as deciduous. 

 The marginal and actinal intermediate plates are also covered with 

 very thin deciduous membrane. There are no abactinal, marginal, 

 or actinal intermediate granules, or pedicellariae. Four webbed 

 furrow spinelets are present, and the first 2 or 3 adambulacral plates 

 have the rudiment of a subambulacral granule. The mouth plates 

 are prominent actinally and each has 7 furrow or marginal spines. 

 The smooth plates and the deciduous membrane would cause this 

 specimen to be placed in the genus Ogmaster if it were adult. It is, 

 in fact, an Anthenoides in an Ogmaster stage. There are no small 

 secondary adradial abactinal plates. 



Specimen No, 2 differs from No. 1 in having 1 or 2 spherical gran- 

 ules on a few of the interbrachial inferomarginals in the position 

 of the future spines, and a very few forcipiform pedicellariae have 

 made their appearance on the actinal intermediate plates; furrow 

 spines 5 or 6. 



In specimen No. 3 the abactinal membrane is thicker and more 

 pulpy ; 2 or 3 small granules have appeared on the proximal supero- 

 marginals and the granules on the proximal inferomarginals have 

 increased to 4 or 5, and are larger, while on the ray a granule takes 

 the place of the small tubercle of the adult. The inner row of the 

 actinal intermediate plates is provided with a central granule (or 

 ?) or 4 on each of the pair back of the mouth plates), while in some 

 specimens of this size a few other intermediate plates may have a 

 central granule; subambulacral granules proximally 2, distally 1; 

 furrow spines, 6. 



In No. 4 minute abactinal granules have made their appearance, 

 which, in No. 5, have increased in number, while in the latter the 

 adult condition is further evidenced by numerous small superomar- 

 ginal granules scattered all over the plate (in No. 4 only a few), a 

 few abactinal pedicellariae, inferomarginal spines, actinal inter- 

 mediate granules on all the plates, and 7 or 8 furrow spines with 

 a furrow pedicellaria on some plates. 



The granules increase in number in the large specimens and the 

 marginal spines become more prominent and more numerous. Inter- 

 brachially there are as many as 6 or 7 in large specimens, and ex- 

 ceptionally 9, some of them beinc: grooved, and bifid. The longest 

 are about 2 mm. On the outer half or third of the ray there is but 1 

 aboral appressed spine to a plate. Sladen figures a terminal plate 



