the Moiyhohgy of the Blastoidea. 225 



Obs. This is a very interesting and peculiar species, rejire- 

 senting, with that next to be described, one extreme type of 

 the genus. The form of the calyx and the angulation of the 

 radial plates Avill readily separate P. cmrjulata from all the 

 described species. The abruptly clavate outline indicates an 

 approach to P. clavata^ Schultze ; but no other resemblance is 

 observable; whilst with P. shnilts (nobis), although after the 

 same general type, no definite comparison can be made. 



There is a curious resemblance in external form between 

 Pentremitidea angulata and Plicenoschisma caryophyUatuM, 

 de Koninck sp., a member of a distinct genus that differs 

 altogether from Pentremitidea in its other characters. Pentre- 

 mitidea anyulata is the aberrant species of the one genus as 

 Phcenoschisma caryo^jliyUatum is of the other. Both agree to a 

 certain extent in outward form, and differ in this particular 

 from the other species of their respective genera. 



Log. and Horizon. Asturias, Spain; Devonian (Mus. Nat. 

 History) . 



Pentremitidea similis, sp. nov. 



/S^;. char. Calyx pentagonal ob]:»yriform, expanding rapidly 

 upwards above the basiradial sutures ; section strongly pen- 

 tagonal, the greatest periphery being nearer the summit than 

 the base; the latter is sharp, and the former depressed. 

 Basals forming a small slightly "expanded cup. lladials 

 arched, broad at their bases, expanding very slightly upwards 

 to the level of the lips, the limbs then rapidly decreasing to 

 the summit, and forming strong projecting lobes around the 

 calyx ; sinuses very narrow, straight, the angle about 134°. 

 Orals almost invisible. Ambulacra narrow. 



Ohs. Although Ave are only able to give a limited definition 

 of this species, it is nevertheless sufficient to show how clearly 

 distinct it is from any other Pentremitidea. On the other 

 hand the resemblance of the calyx in general form to that of 

 an Orophocrinus^ especially that of the typical species O.stel- 

 Uformis, is very remarkable ; but here, of course, the resem- 

 lalanee ceases. The radial angle, the length of the ambulacra, 

 and the greater amount of calycular surface between their 

 distal extremities and the base of the calyx in P. simih's 

 separate it from P. clavata, Schultze, to which it is nearly 

 related. The form of the radial plates in P. anyidata, irre- 

 spective of other characters, at once separates the latter from 

 P.similis. The ]\Iessrs. Sandbcrger have described a peculiar 

 form from the llhenish Devonian rocks, which is much too 

 de])ressed a species to be confounded witli ours, even supposing 

 the former to be a Pentremitidea. 



Loc. and Horizon. Eifel ; Devonian (Mus. Nat. History). 



