Gutty Marine Laboratory , St. Andrews. 171 



from Greeiilatul ami Canada (P. tninuta, Fabr.), compara- 

 tively little difference is observed, both having from 18 to 23 

 moniliform cilia externally. 



The j)osterior scales in var. inornafa become still more 

 elonpfated transversely, have only about 6 of the larger 

 moniliform cilia on the abbreviated external border as well as 

 the posterior edge. 



On the whole, therefore, the study of the scales supports 

 the view that P. tninuta, Fabr., and Dr. Johnston's P. iaornata 

 are the same sj)ecies. 



In the variety eximia of Dr. Johnston the first pair of 

 scales are similar in shape to the foregoing, though from the 

 smaller size of the examples they are considerably less. The 

 outer border has a series of longer cilia, fewer in number, but 

 similar in structure. They encroach somewhat on the ante- 

 rior border, or, rather, a few of the isolated cilia scattered 

 over the surface project beyond tlie edge. None of the 

 smaller clavate cilia so cliaracteristic of the two foregoing 

 varieties are present on this edge. The large isolated cilia 

 occur both externally and posteriorly to the scar for the 

 elytrophore. The second pair of scales are distinguished by 

 the greater length of the cilia on the outer border. A few 

 also occur along the posterior edge. 



The succeeding scales of the anterior third do not differ 

 much in shape from those of P. minuta, but tiie cilia are 

 much longer and stand stiffly out on the external margin and 

 the outer half of the posterior edge. They are less numerous 

 than in the large examples of P. inornata, but agree with the 

 smaller in this respect. The posterior scales have about the 

 same number of cilia as P. inornata, but they are stiffer and 

 longer. P. eximia is distinguished externally from P. in- 

 ornata in spirit by the olive spot with a pale centre in each 

 scale at the scar for the elytrophore. Occasionally in certain 

 forms oi eximia, e. g. from Lochmaddy, North Uist, the cilia 

 on the scales are fewer, longer, and without the terminal 

 enlargement. 



The second foot (first bristled) in P. inornata is bifid, with 

 two well-developed spines. The dorsal lobe forms a rounded 

 eminence with a smooth surface, from which project the com- 

 paratively short, slender, minutely spinous bristles, with a 

 very fine hair-like tip. The inner forms taper more abruptly 

 than the outer, and the tips are often bent nearly at right 

 angles to the base. The ventral lobe is longer, bluntly 

 conical, and with numerous small papillae on its surface. The 

 ventral bristles have stout shafts, dilated at the tip, and with 

 numerous rows of spines on the convex margin, thus differing 



