318 PROCEEDINGS OF THE ACADEMY OF [1890. 



The liarbor of Vera Cruz i.s an area of luxuriant coral growth, 

 madrepores and brain corals being especially abundant.' No holo- 

 thurians were collected here, but on the other hand two species of 

 (jphiurans were obtained. The forms from this locality are the fol- 

 lowing: Diddema sefosum, Echinometra subangularis, Mellita jicnta- 

 2)orns, Thyraster serpentarius, Astropeden articulatus, Ophiura ciii- 

 erea and Ophiothrix angulata. 



After the detailed account of the species collected which follows, 

 in which they are separated into the two regions from which they 

 were obtained, I have advanced some general considerations based 

 upon their geographical distribution. A chronological list of all the 

 important memoirs dealing with the Echinoderms of the West In- 

 dian region, has also been compiled which I believe will be of use 

 in the future study of this area. 



Yucatan. 



Holothuria Heilprini, n. s]>. PI. VIII, figs. 1-6. 



Body cylindrical, narrowed toward the anterior end. Specimen 

 very much contracted, probably to half the length of its extended 

 condition. Anus round. 



A few large wart-like prominences scattered over the dorsal 

 surface, each surmounted by a papilla containing a rudimentary 

 terminal plate and smooth rib-like rods with the ends enlarged and 

 perforated. Pedicels present upon the dorsal and ventral surfaces : 

 upon the dorsal surface they are evenly distributed and are slightly 

 smaller than those of the ventral surface. The ventral pedicels 

 are very numerous and closely approximated. In the specinien 

 collected there is no trace of a linear arrangement. 



The specimen obtained has ten tentacles, the most ventral of which 

 is much smaller than the rest. 



The body wall is very thick in the much contracted example. 



The calcareous ring is very similar to the figure of that of 

 Holothuria Floridana given by Selenka^ in his " Beitriige." 



There are two bundles of short madreporic canals attached to 

 the dorsal surface of the oesophagus on the right and left sides 

 respectively of the dorsal mesentery. In the specimen ubtained 

 there are twenty canals on the right side and nineteen on the left. 



^ See Professor Heilprin's Report upon " The Corals and Coral Reefs of the 

 Western Waters of the Gulf of Mexico " in this volume, p. 303. 

 2 Zeit. wiss. Zool. Bd. xvii, pi. xviii, fig. 47. 



