OF ARTS AND SCIENCES. 203 



Cottaldia Forbesiana, A. Ag., nov. sp. 



There is only a single specimen of this interesting species (probably 

 not full grown). It is closely allied to the tertiary Psammechinus 

 monilis ; pores are arranged in simple vertical rows, much as in Temne- 

 chinus. The spines similar to those of Salmacitlae ; large abactinal 

 system of Temnopleurus, without, however, any trace of the indentations 

 and pits of the Salmacidoe and Temnopleuridag. Actinostome sunken, 

 actinal membrane covered with ten large plates, spine white or a yel- 

 lowish orange, primary tubercles of the same size in both areas, form- 

 ing a very marked vertical row in the ambulacral area ; secondaries 

 forming indistinct horizontal rows near the ambitus, genital opening 

 small, sharply cut ; genital plates crowded with secondaries, anal sys- 

 tem covered by few plates. — Station 173, 315 fathoms. 



Trigonocidaris monolini, A. Ag., nov. sp. 



This species is readily distinguished from T. albida by the structure 

 of its actinal membrane and the striking ornamentation of the genital 

 ring, and the relatively smaller number of primary coronal plates and 

 coarser pitted reticulation, both in the ambulacral and interambulacral 

 areas. The ten buccal plates occupy nearly the whole of the distal 

 edge of the actinal ring, while in T. albida they are small and the 

 actinal membrane is crowded by imbricating plates. A prominent 

 ridge extends round the edge of tbe ocular plates and across the ad- 

 joining genital plates, forming a pentagon with rounded angles round 

 the anal system ; two or three prominent secondary tubercles are 

 placed in the middle of the genital plates. No similar ornamentation 

 in found in T. albida. — Station 170, 520 fathoms. 



Echinus horridus, A. Ag., nov. sp. 



Fragments and imperfect specimens of a large conical Echinus were 

 collected in the Straits of Magellan which cannot be referred to any 

 of the species already known from that locality. It seems to be read- 

 ily characterized by its narrow poriferous zone. One principal row 

 of primary tubercles in the interambulacral space, with secondaries in 

 irregular diverging lines from it ; the spines are remarkable for their 

 length, even comparatively much longer than in some specimens of 

 E. acutus; abactinal system very compact; large genital plates, small 

 ocular plates. Actinostome small, not as large as abactinal system ; 

 color of test reddish brown when dry, spines darker color. — Off Tom 

 Bay ; Station 308, 175 fathoms. 



