Handbook of Paleontology 123 



The tide pools have their characteristic life. Besides 

 the algae already discussed, there are other forms to be 

 noted. Incrusting red seaweed (Hildenbrandtia) often 

 carpets the pools, and it is also common everywhere on 

 stones and rocks at low water. Interspersed one often 

 finds the deep red color of another incrusting form 

 {Petrocelis cruenta) which is common north of Cape 

 Cod. The lime- secreting red alga resembling coral 

 (Corallina) has already been described. Also to be 

 noted are the fine feather}- plumes of a brown seaweed 

 {Desmwest'm), the fan-shaped fronds of a purplish red 

 seaweed known as Dulse, and more delicate tufts of red 

 and brown seaweeds. There likewise occur in these 

 pools, typically along the Xew England coast, green, gela- 

 tinous, fleshy balls, looking like small green tomatoes, 

 one and one-half to two inches in diameter. These are 

 green algae (Leathesia difformis) which grow in bunches 

 on other seaweed and on sand-covered rocks, and are 

 found in summer on every coast. The balls are hollow 

 and also become lobed and hollow. The vegetation of 

 rock pools differs according to the situation within the 

 tidal range, the geological nature of the rock, size, depth, 

 drainage, illumination etc. In the upper pools the incrust- 

 ing forms are conspicuous. Plant life becomes more 

 abundant where there is a more gradual slope and the 

 sides are rougher and more irregular. The higher the 

 elevation of the pool, the fewer the species, but there may 

 be a greater number of individuals. 



Rock pools solve the problem for typically marine 

 forms on rock}- shores. Besides the algae discussed 

 above, there are sponges, hydroids, bryozoans, nudi- 

 branchs, echinoderms, mollusks and crustaceans. Some 

 of the more common representatives will be touched 



