3f)8 CLYPEASTER SUBDEPRESSUS. 



tioned by various writers on Echinoderms, but it has invariably been pre- 

 sumed to be founded upon mistaken localities (Peronclla decagonalis) or a 

 confusion with young specimens of Clypeaster subdepressus. Mr. Pourtales 

 has dredged, from a depth of thirty-four fathoms, a small Clypeaster subde- 

 pressus of about two inches in length, which has the facies of a Laganum 

 (PI. XIII. f. 16-18) to such an extent that it would pass for one without an 

 examination of the internal structure. The outline is pentagonal, with 

 rounded corners ; the pentagon is equilateral, and more regular than in any 

 species of Laganum, the central part of the test rising abruptly from the 

 extremity of the ambulacra! rosette, which is not swollen. The petals are 

 opened at the extremity. In this } 7 oung specimen the lower surface is 

 covered with spines only upon the interambulacral and a part of the am- 

 bulacra] area, leaving broad, bare bands of the ambulacra! areas colored 

 light yellow, giving this specimen a striking appearance. The tubercles 

 of the upper part of the test are quite small, closely crowded together; 

 they increase in size in the interambulacral spaces of the lower surface. 

 The color of the spines is greenish-yellow. Tin' test has a thick, rounded 

 vi\'jn\ and it may he that specimens of this shape have been collected by 

 those who have referred to the presence of a Laganum in the West India 

 Islands. Ilupe speaks of Laganum latissinuun as found on the coast of 

 Brazil. His specimen is nothing hut the extremely fiat variety of this 

 species, of which I have also seen specimens from Cuba in the collec- 

 tion of Mr. R. A ran go. 



Liitkcn has given an excellent figure of young of this species (Bidrag. til. 

 Kundskal) om Kchiniderne, PI. //. /'. s>)'. Mr. Pourtales has dredged young 

 specimens, one younger ( in this youngest specimen the ambulacral rosette 

 was already developed, PI. XIII. /'. W) than the one figured by Liitken, 

 and the other slightly older. The specimens can at once he recognized as 

 young of C. subdepressus by their short ambulacra! rosette and their sunken 

 aetinostomes. The comparatively thick rounded edge of these young speci- 

 mens gives them a striking resemblance to Laganum. In the oldest of these, 

 and in one measuring only a trifle over ~>l mm in longitudinal diameter, col- 

 lected at Charleston, we have already the general elongated outline of the 

 adult, hut the edge of the test is much thinner and the ambulacral rosette 

 more closed than hi the adult. The tubercles are scattered uniformly over 

 the test, and we do not find, as in the younger specimens, along the edge 

 of the test, larger tubercles in five or six irregular horizontal rows, giving to 



