196 Mr. J. Miers on the genus Pionandra. 



P. latus, it descends from them and joins the marginal fasciole 

 below their base, so that the anterior sides of the antero-laterals, 

 and the single ambulacrum, want the peripetal fasciole. The 

 specimen before us is so much crushed, that we cannot trace the 

 band continuously all round the test, so as to describe its course 

 with accuracy ; it is possible that this species may form the 

 type of a distribution of the fascicles distinct from any that is yet 

 known. We have stated enough to show, that at least in this form 

 there is a considerable deviation from the normal arrangement. 

 The anus is large and oval, and near the dorsum; the mouth is wide 

 and bilabiate, and situated near the border ; the sternal portion 

 of the interambulacrum is slightly convex, and thickly covered 

 with an imbricated arrangement on the plates, on each of which 

 a perforated tubercle is raised. The basal poi'tions of the inter- 

 ambulacral pairs are covered with wider-set tubercles of the same 

 size, and the entire upper surface of the test is crowded with small 

 tubercles closely set together, and very uniform in size and 

 arrangement. The mouth is surrounded by five petaloid pori- 

 ferous ambulacra. 



Affinities and differences. — The excentrical position of the disc, 

 with its four genital holes, and the petaloid poriferous ambulacra 

 around the mouth, establish an affinity between this form and 

 Brissus. The way in which the peripetal joins the marginal 

 fasciole is similar to what exists in Schizastei-, whilst the mar- 

 ginal fasciole, entirely encircling the test and passing round 

 beneath the anus, is found only in Pericosinus. The excentral 

 position of the apical disc and the shallowness of the am- 

 bulacral star foi-m a sufficient diagnosis between this species and 

 P. latus. 



Locality and stratigraphical position. — Collected from bed 

 No. 1, the Gozo marble at Malta, where it is rare. 

 [To be continued.] 



XVII. — On the Genera Pionandra, Cliocarpus and Psecilochroma. 

 By John Miers, Esq., F.R.S., F.L.S. &c. 



Pionandra. 



The details of this genus as given in Lond. Journ. Bot. iv. 353, 

 and in 111. South Amer. Plants, i. 31.pl. 8 & 9, were first drawn 

 up during my stay in the Organ Mountains in 1837, but not 

 pubHshed till 1845, and while these were in type, Dr. Sendtner 

 contributed to the Munich flora his genus Cyphomandra, iden- 

 tical with the above, so that by a month's priority in publication, 

 the latter name has claimed the preference. I there divided 

 Pionandra into two very distinct sections. 1. Ceratostemon, 



