Nc7C' species aud New Sir uc I ma I Parts of Fossils. 87 



Hoi,ocYSTrri';s afi'inis, n. sp. 



Plate /, Fig. 16, anterior side vica' ; I'ig. //, posterior side 

 vic7c ; Fii^. /<S', sininiiit viejc. 



Species nicdiuni size, sessile, subovate to sn1)j^lol)ose, pos- 

 terior and left side more tuinid than the anterior and right 

 side, and the most tiiniid part is below the middle. There are 

 al)out seven ranges of plates of unequal size and a few inter- 

 calated ones. The mouth is large and a little anterior to the 

 central part of the summit. Ambulacral orifice near the pos- 

 terior central part of the summit, and surrounded with four 

 prominent arm bases. All the plates are ornamented with 

 large pustules, and pierced with numerous pores. There are 

 a number of the large circular openings or pits irregularly 

 distributed on various parts of the test, like those described 

 on //. eleganSy H. rotundiis and H. iurbiiiatus, the economy of 

 which has not been ascertained, and which may represent 

 only a diseased test. 



It would seem to be most nearly related to such forms as 

 H. ornatissinius and H. subovatus, but a comparison with the 

 illustrations will show it is distinguished by its form and the 

 location of the mouth and ambulacral orifice, as well as by the 

 number of the plates and by the circular pits, if that charac- 

 ter indicates a specific difference. These pits cross sutures 

 and ma}' embrace the angles of three or four plates, or they 

 ma}' be embraced wholly within a plate ; when they cross a 

 suture the suture seems to disappear and the plates at that 

 place are anchylosed. This anchylosis and some of the rock 

 which adheres to the specimen illustrated has prevented us 

 from correctly outlining all the plates. The Holocystites are 

 so variable in all respects that it is hard to tell exactly what 

 should be considered specific characters and what should be 

 regarded as variations among fossils belonging to the same 

 species. 



Found in the Niagara Group, near Madison, Indiana, and 

 now in the collection of Mr. Faber. 



