PLEIOCENE FOSSILS. 5 



AGASSIZIA.— Val. 

 AGASSIZIA PORIFERA.— McCeady. 



Plate I., Fig. 5, and Plate IT., Fig. 4. 



Brissopsis porifera, Bavenel, Catalogue of Echinidse Eec. and Foss. of So. Ca., p. 4, et fig. 

 Charleston. (1848.) 



Species magna, lata, alta, paene globosa, tamen postice truncata; inter-ambulacris summis 

 gibbosis • apice sexuali mediano ; ambulacris paribus posterioribus longis, et extremitates 

 animalis periplieriem versus leviter curvantibus ; ambulacris anterioribus prope rectis, et 

 omnibus non profunde impressis ; poris ambulacribus plusve minusve rotundatis et semi- 

 ambulacro obliterate- totam ejus longitudinem non facili visu ; impressione seufaciola later ali 

 impressionis peripetalis angulum infimum incurrente ; tuberculis maximis anteriorem testam 

 densis. Infra, sterno lato • ambulacris posterioribus angustis, et testae periplieriem versus 

 arcuatis et posterioris regionis tuberculis maximis longum spatium densis. 



Description. This large species exceeds the A. excavata (Val.) in height, but it is not 

 conical like Brissopsis rimulata (Rav.) of the Eocene, which is also an Agassizia. It is 

 more nearly spherical than either of those two species, having, however, a truncated 

 appearance posteriorly from the great relative size of the Anal Facet. The upper ends of 

 the inter-ambulacra are quite bulging. The sexual centre nearly median. The hinder 

 paired ambulacra long and slightly bent outwards at their peripheral ends. The anterior 

 paired ambulacra are nearly straight and have their obliterated half rows of pores scarcely 

 perceptible for their whole length. The ambulacral pores are more or less circular in 

 outline. The side-belt joins the outer star-belt at its lowest angle or elbow, and the fore- 

 shell is thickly strewn with the greater sized knops. On the nether surface, the breastplate 

 is broad, and flanked by very narrow ambulacra, which are also somewhat bowed outwardly 

 towards the outline of the shell, and are covered to an unusual extent posteriorly with 

 large tubercles. 



The specimen from which this description and figure are taken, is the only one yet 

 brought to light, and was found by Dr. Ed. Ravenel, at his plantation, the Grove, Cooper 

 River, in a bed of Pleiocine Marl. In his catalogue it is registered as a Brissopsis — the 

 want of specimens and diagnoses of the two genera, at that time, precluding the possibility 

 of his accurately determining its generic position. He generously placed it in my hands 

 for description. It is, beyond doubt, an Agassizia, as is shown by the arrangement of its 

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