156 THE FOSSIL ECHINOIDEA 



to the same degree as in the anterior petals. At the widest part of the posterior am- 

 bulacra, where the petal measures 7 millim. across, the interporiferous area is 4 millim. 

 in breadth, and the poriferous zone is 1'50 millim. broad: from this point the zone 

 diminishes in breadth to the outer extremity, where it is little more than half the 

 width named, and less than 1 millim. across. At the outer extremity of the petal the 

 interporiferous area measures 4'25 millim. across. The inner pores are round, the outer 

 transversely oval, and they are united by a broad conjugating groove. The costse are 

 low and narrow, with a well-defined single row of about seven small miliary granules ; 

 and the positions of the costse and the pairs of pores are oblique in relation to the 

 median line of the ambulacrum. The extra-petalous continuations bf the poriferous 

 zones are scarcely perceptible until near the peristome, and are not placed in any 

 channel on the actinal surface. 



The interporiferous area within the petal is almost flush with the test, being very 

 faintly tumid ; and its ornamentation, which is similar to that of the interradia, is rather 

 more ornate than usual in this genus. It consists of small primary tubercles placed in 

 rather large and shallow scrobicules, which are surrounded by a single circlet of rather 

 large, well-spaced, and comparatively isolated miliary granules. From these not forming 

 the ordinary confluent ornamentation usual in the interspaces between the scrobicules 

 in this genus, and from the small size of the primary tubercles, the general ornamen- 

 tation is well characterized in the present species. At the ambitus and on the actinal 

 surface the scrobicules are very closely placed, with not more than a single row of miliaries 

 between each ; but in places on the abactinal surface they are rather more widely spaced. 



The peristome is slightly excentric in front ; it is, unfortunately, too much obscured 

 by matrix for any remarks to be made on its structure. 



The periproct, which is of moderate size and transversely oval, is placed close to 

 the posterior margin of the test, its aboral margin encroaching slightly thereon. The 

 major diameter measures 10 millim., the minor diameter being probably little more than 5. 



Memarks. This species has some resemblance to JE. rotunda, but is readily 

 distinguished by the different form and proportions of the test, by the narrow and 

 apically-pointed and attenuate ambulacra, which are unequal and do not converge at 

 their outer extremity, as well as by the different character of the ornamentation. 



From E. scutiformis, Desm., it differs in the form of the test, the absence of the 

 posterior rostration, the greater excentricity of the apical disk, and in the character of 

 the ambulacra. It is likewise easily separated from E. Studeri, Agassiz, E. Escheri, 

 Agassiz, and E. globulus, Laube, by the form of the test atid the shape of the ambu- 

 lacra, as well as by other points. We are unacquainted with any other Echinolampad 

 with which it can be confounded. 



Mmensions. 



millim. 



Length of the test 65 



Breadth of the test 56 



Height of the test 33 



Breadth of the postero-lateral petal .... 7 



„ „ antero-lateral petal .... 6 



