244 BULLETIN OF THE 



half-grown 0. fragilis, although it is said to have been brought from the 

 Pacific by Escholtz. 



It will be best next to speak of the European OpMothrix most unlike that 

 just described. In Naples, Dr. Gasco showed me a large number of living 

 Ophiothrices, and called my attention to their great differences. One sort was 

 blue with a swelled body, short arms, and rather stout arm-spines; the other 

 was reddish-brown, with a flat rounded disk and slender spines on it, and long 

 arms, by whose rapid worm-like motion the animal slid briskly over the bot- 

 tom of a basin tilled with sea-water. This latter is the species identified by 

 Liitken as Asterias quinquemaculata of Delle Chiaje. Here it is proper to say 

 that the descriptions and plates of that Italian author, so far as concerns 

 Ophiurans, are utterly unrecognizable ; the figures, in fact, portray animals 

 that do not exist anywhere. However, to avoid multiplying names, there is 

 no objection to taking the nomenclature of Delle Chiaje and applying it arbi- 

 trarily to Mediterranean species. Unlike most Ophiurans, this species is 

 better marked as young than as adult, when it bears some resemblance to O. 

 pentaphyllum (to be described further on). With a disk of 3.5 mm. the arm 

 was already 25 mm. long, or in proportion of 7:1, which is greater than I 

 have usually found, even in the full grown of other European species. The 

 disk was fiat and circular, little lobed, and bad its surface regularly spriukled 

 with minute, equal, slender, trifid stumps, with sometimes none on the radial 

 shields and sometimes as many as four (PI. II., Eig. 4G), also there were long, 

 thin, cylindrical spines, as long nearly as those of the arm, having very small 

 thorns on the sides and tip ; these spines were all articulated on little 

 mamelons, on which they have a free motion (Fig. 4 7), a character I have 

 not observed in the other European species. There were but six arm-spines, 

 the two upper ones longest, viz. 2.7, 2.5 mm., with a glassy look and nine- 

 teen thorns on each edge. A specimen, whose disk was 7 5 mm. in diameter, 

 had stouter forked and trifid stumps on the centre (Fig. 52) ; stouter articu- 

 lated spines ; and, on the edge of the disk, much elongated forked stumps 

 (Fig. 53). An individual with a disk of 9 mm. resembled the young one first 

 mentioned, except that the disk spines were of several sizes, and the upper 

 arm-plates, of course, proportionally wider. There were six or seven arm- 

 spines, whereof the longest was 4.5 mm., with as many as twenty-five or even 

 twenty-seven thorns on each edge. A large specimen had the disk 14 mm. 

 in diameter, flat and circular, with large smooth radial shields, resembling in 

 these respects 0. pentaphyllum ; besides the long articulated spines (Fig. 51), 

 there were in the centre numerous short, thick stumps, with crowns of three 

 or four long thorns (Figs. 49, 50), or conical grains with thorns on top (Fig. 

 48) ; while near the edge and below were very elongated clavate stumps (Fig. 

 54). This was the usual armature in a large number of adults, some with 

 the disk as large as 16 mm.; the differences were in the proportion and 



