NORTHUMBERLAND AND DURHAM. 1 1 9 



On shells, &c., from low -water mark to deep water; not 

 uncommon. 

 Deep-water specimens of this beautiful and delicate species 

 sometimes reach the height of five or six inches on our coast. 



4. P. SETACEA, Ellis. 



Johns. Brit. Zooph., 97, t. xxii., f. 3 — 5. 

 On Laminaria digitata and other sea-weeds at low-water 

 mark and in shallow water ; frequent. 

 P. setacea seldom, if ever, exceeds an inch and a-half in height 

 in this locality. 



5. P. ECHiNULATA, Lamh 



Johns. Brit. Zooph., 464, wood-cut 80. 

 On stones between tide-marks, and on the roots of Lamina- 

 ria digitata ; not rare. Cullercoats and Ryhope. 

 This species appears to be more widely diffused than was at 

 first expected, but has been passed over as a small variety of one 

 or other of the two preceding. The three species are so nearly 

 allied that some little care is required in discriminating them. 

 The number of joints in the stem and pinnae, and the curious 

 trumpet-shaped processes or tubules, afford the most reliable 

 characters. P. echinulata is rather robust, compared with the 

 other two, and is always of humble growth, scarcely rising above 

 an inch from a strong, creeping root-fibre, on which the ovicap- 

 sules are profusely developed. It differs from P. j)innata in hav- 

 ing a joint of the stem above each pinna, in which it agrees with 

 P. setacea^ hvit it differs from P. setacea, and agrees with P. jnn- 

 nata, in having generally only one joint of the pinna between 

 the cells ; P. setacea has always two. There is now and then an 

 additional joint developed in parts of P. echinulata. P. ^nnnata 

 has one short, small tubule below each cell ; P. echinulata has the 

 same, but has an additional one behind and above the cell. 

 P. setacea has two longish tubules below each cell (one on each 

 joint), and two abreast behind and above the cell: there is also 

 a tubule on each joint of the stem, on the opposite side to the 

 pinna, which is not the case in either of the other species. Wlien 



VOL. III. PT. 11. p 



