Narrative of Bahama Expedition, 



45 



still water. These overarching" rocks are fairly alive on their 

 under surfaces with peculiarlv hideous crabs. Graf)siis iiiani- 

 latus Calcshy.^ called •• rock crabs" b\- the natives, but not the 

 rock crabs of our northern shores. These are remarkably 

 flattened forms with conspicuous stripes in regular patterns 

 over the carapace and appendages. The facilit}- with which 

 thev run along, clinging to the under surfaces of rocks, is 

 amazing. It is exceedingly difficult to catch them e\'en with a 

 dip-net, so long as they are out of the water, but we found 

 that b\' forcing them to drop from the rocks thev could be 

 scooped up with comparative ease. 



The handsome gasteropod Lizoiiia pica is found in abund- 

 ance, clinging to the under side of these overarching rocks, and 

 most of the species found on the rocks in the cove at Egg 

 Island were also encountered on Little Egg Island. 



Six or eight species of serpent stars were collected here, 

 among which was a remarkably pretty blue Ophiothrix. an 

 exquisite object under the lens, with its glass}' serrated spines 

 and beautifully colored disk. The genera AuipJiiura and 

 Auip]iiu)ua were also represented. Here, too. our students 

 first collected that striking but onlv too common sea-urchin 

 Diadema setosiiiii. with its exceedingly long and sharp spines, 

 from which man\' a painful wound was received by our col- 

 lectors during the cruise. 



Quite a number of Gorgonidiv were secured, the most con- 

 spicuous being the common sea-fan. Rhipid{u,vroia flidKlhiin. 

 It is hard to see what has prevented authors from separating 

 the red and yellow '• varieties " of this gorgonian into two 

 species. The difference in color seems absoluteh' constant, 

 and there is also a marked difference in size, the purple form 

 being decidedlv the larger on the average. A constant differ- 

 ence both in size and color would seem to be sufficient for spe- 

 cific distinction. It is also a fact worth noting that the two 

 varieties do not usually grow together, but in communities in 

 which one or the other is exclusix'ely foimd or greatly pre- 

 dominates. 



1 Miss Mary E. Rathlmii, of the .Smithsonian Institution, lias very kindly identi- 

 fied most of the hrachyuran cral)s nicntioned or H<jnre:l in this narrative. 



