REPORT OF THE ECHINOIDEA—MORTENSEN 113 
Family MICRASTERIDAE 
ISOPATAGUS, new genus 
Large forms of high, rounded-conical shape; oral side slightly con- 
vex. Test fairly strong. Ambulacra all equally developed, petaloid, 
slightly sunken. ‘The pores remain distinct from the distal end of the 
petals to the edge of the test. Anterior end of the test rounded, not at 
all sunken. Apical system shghtly anterior, ethmophract, with three 
genital pores. Mouth very near the anterior end, with fairly promi- 
nent labrum. Periproct inframarginal, very small, of ovoid outline. 
Test densely tuberculated with very small, uniform tubercles. Spines 
uniform, smooth, only about 5mm. long. No fascioles. Pedicellariae 
of only the tridentate and triphyllous types. Color dark purplish, 
the denuded test whitish. 
Genotype: Jsopatagus obovatus, new species. 
This interesting genus is nearly related to the Cretaceous genus 
Isaster Desor, of the Micraster group, no recent forms of which were 
known till now. 
ISOPATAGUS OBOVATUS, new species 
Locality —Station 5425, Sulu Sea (lat. 9°38’ N., 121°11’ E.) ; 907 
meters; March 31, 1909. Four specimens, one of them very badly 
broken, but the fragments could be fitted together so as to form a 
tolerably complete specimen. 
Type.—U.S.N.M. No. E.7149, from station 5425. 
Description—The diagnosis of the genus applies equally well to 
the species, this being the only one so far known. It need only be 
added that the tridentate pedicellariae have slender valves, some- 
what involuted in the lower part of the blade; the epiphysis usually has 
a small prominence at its upper end. They are on the whole small and 
very inconspicuous, hardly exceeding 0.5 mm. in length of head. 
Family PALAEOPNEUSTIDAE 
Genus ARGOPATAGUS A. Agassiz 
ARGOPATAGUS VITREUS A. Agassiz 
Argopatagus vitreus A. AGAssiz, Challenger Echinoidea, p. 160, pl. 32, figs. 1-6, 
1881.—H. L. Crark, Hawaiian and other Pacific Echini, Echinoneidae ... 
Spatangidae, p. 146, 1917. 
Phrissocystis humilis DE MEIsERE, Siboga Echinoidea, p. 198, pl. 10, figs. 99, 100; 
pl. 28, figs. 494-500, 1904. 
Meijerea humilis DOvERLEIN, Echinoidea d. deutschen Tiefsee-Exped., p. 2438, pl. 
31, figs. 1-4; pl. 49, fig. 7, 1906. 
Meijerea excentrica A. AcAssiz and H. L. CriarK, Bull. Mus. Comp. Zool., vol. 
50, p. 252, 1907 ; vol. 51, p. 132, 1907. 
781385—48——4 
