1863.] DUNCAN WEST INDIAN COEALS. 429 



not dentate, upper border; it is perfect in a considerable part of 

 the specimen, and the sides of the lamina are finely granular. Septa 

 numerous and crowded, in six unequal systems. There are four 

 cycles in two systems, in two systems five, minus certain orders, and 

 in the remaining systems the fourth and fifth orders are wanting in 

 half of each system. 



In 2 systems there are 8 septa =16 

 In 2 ' „ „ „ 13 „ =26 

 In 2 „ „ „ 6 „ =12 



54 septa. 



The primary, secondary, and tertiary septa are very much alike, 

 and project but little. They are all slightly arched, and rather 

 stouter nearer the wall than internally. They are faintly granular, 

 and their orders may be recognized with care. The septa of the 

 higher orders are very delicate ; all correspond to faint costae, and 

 the primary septa at each extremity correspond with the large costae. 

 Height 4- inch. 



Prom the Nivaje shale. Coll. Geol. Soc. 



As a species of the Turbinolides without pali and with an epitheca, 

 this specimen might be considered a Flabellum closely allied to F. avi- 

 cula (Turin, Miocene) ; but the laminar columella places it in the 

 genus Placotrochus. Its compressed form, lateral crests, irregular 

 septal arrangement, small basilar spot, and angular calicular mar- 

 gins are very distinctive of the species. The basilar spot is not a 

 concave fracture, but a plane rupture as in Flabellum spinosum. 

 The great angle formed by the costae is equally a peculiarity of the 

 genus Flabellum, and, close as Placotrochus is to that genus (differing 

 in the important laminar columella), the form from San Domingo con- 

 nects the two more intimately than the species Placotrochus Icevis and 

 Placotrochus Candeanus, both of which are recent, the first from the 

 Philippines, and the second from the Chinese Seas. 



The alar costae and the small base of Placotrochus Lonsdalei distin- 

 guish it from Placotrochus alveolus (Jamaica, Miocene). I have 

 named this beautiful little form after Mr. Lonsdale, who noticed the 

 existence of the genus in the Heneken Collection, in his brief sum- 

 mary of the San-Domingan fossil Corals already noticed. 



5. Plabelltjm dubitjjU, spec. nov. 



Corallum simple, in the form of a slightly compressed cone, 

 straight. Epitheca incomplete, pellicular. Base small and conical. A 

 mark of attachment is visible, there being two fractured appendices on 

 one side of the base, one of which corresponds to the long axis. Costas 

 not crested, none larger than the majority. The lines of the costae 

 at the ends of the long axis form less than a right angle, or about 

 70°, where they join at the base. Long axis about one-third longer 

 than the height of the corallum ; length I! inch. Length of the 

 short axis 1 inch ; its plane is a little higher than that of the long 

 axis. Calice elliptical ; fossa shallow at the sides, and deepening in 

 the middle. Septa rather exsert, delicate. Primary, secondary, and 



