638 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.54. 



on the dorsal side of the disk and to the exclusion of the character- 

 istic hooks on the dorsal side of the arms as far as the seventh 

 branching it is absolutely unique. 



ASTROCYNODUS, new genus. 



Genotype — Astrocynodus herrerai^ new species. 



Diagnosis. — Five madreporic plates, one in the innermost corner 

 of each interradius; tentacle papillae present from the second arm 

 branch onward; eight or nine arm divisions; each arm segment as 

 far as the seventh fork bears a conspicuous transverse band of closely 

 appressed tubercles, each carrying an articulated conical tooth; the 

 ribs of the disk bear numerous similar transverse bands; from the 

 seventh fork onward each arm segment bears a double transverse 

 row of closely appressed tubercles, each carrying a slender very 

 strongly recurved glassy hook without accessory prongs ; teeth, tooth 

 papillae and mouth papillae very long, subequal. 



Distribution. — Only known from the Caribbean Sea. 



Depth. — Shallow water. 



Included species. — Astrocynodus herrerai. 



For the privilege of making known to science the following re- 

 markable new species the museum is indebted to the kindness and 

 generosity of Prof, A. L. Herrera, the director of the National 

 Museum of Mexico: 



ASTROCYNODUS HERRERAI, new species. 



Plate 96. 



Description. — The disk, 52 mm. in diameter, is rather deeply in- 

 cised interradially. There is no peripheral girdle of plates. The 

 ten radial ribs stand out prominently. 



Aborally the disk is entirely covered with extremely small grains, 

 very closely crowded, which become larger toward the periphery and 

 are largest on the outer half of the ribs. In their inner halves the 

 ribs bear about 10 more or less regular cross bands, each consisting 

 of a single row of closely crowded and regular tubercles, considerably 

 larger than the adjacent grains, each of which carries a short stout 

 blunt conical spinelet or tooth attached to it by a movable articula- 

 tion. On the outer half of the ribs these cross bands become some- 

 what more separated and irregular, breaking up into sections or 

 running diagonally across the rib, and the conical articulated teeth 

 which they bear become longer and more sharply pointed, though 

 never exceeding half a millimeter in length. The ends of the ribs are 

 occupied by an oval shield about twice as broad as long, covered with 

 finer grains than those on the adjoining body surface. Between the 

 ribs there are a few irregular patches of enlarged grains, and in the 



