249 
thai) the two above. One of these is the Palmipes lobianci Ludw., 
wkich represents, according to Ludwig, most probably a hybrid 
between Palmipes membranaceus and Asterina gibbosa l ). The other 
case is mentioned by Verrill (Op. cit. p. 544), who reports the 
rather common occurrence at Sitka a. o. places on the North 
American West Coast of hybrids between Asterias e.piddora (Br.) 
and Pisaster od,racens (Br.), the former being a small, usually 
six-rayed, diplacanthid species, the latter a large, coarse, five-rayed, 
monacanthid species. Verrill also suggest the existence of hybrids 
betweeu Asterias epichlora and A. hexaetis (St.), and of either of 
these species with Asterias Troscheli (St.). It would then appear 
that this region is unusually favourable for the study of hybridism. 
') H. Ludwig.. Die Seesterne des Mittelmeeres. Fauna u. Flora d 
Golfes v. Neapel. 24. Monogr. 1897. p. 267. Professor Ludwig has 
kmdly called my attention to tilis form, which I had forgotten. 
Explanation of Plate IV. 
lig. 1. Asterias robens L. Abnormal specimen from the Isefjord. 
2. Asterias Malteri var. gronlandica Stp. Abnormal specimen from 
Greenland. 
3. Astropecten irregularis (Penn.). Abnormal specimen from the 
coast of Bohuslan. 
4. Ceramaster (Pentagonaster) granularis (Retz.). Abnormal spec- 
lmens from the Trondhjemsfjord. 
— 5. Ophiura (Ophioglyphaj Sarsi Ltk. Abnormal specimen from the 
Northern Stromfjord, Greenland. 
— 6. Ophiura ( Ophioglypha) albida Forbes. Abnormal specimen from 
the northern Kattegat. 
All the figures are represented in natural size. 
22.-5.-1913. 
16 a 
