60 TROPICAL PACIFIC ECHINI. 
The spines of the miliaries are serrated, smaller in size and of even diameter 
up to the distal end where they thicken, and each rod ends in a sharp point. 
Those found on or close to the actinostome are nearly one millimetre in length, 
and diminish until in the apical system they are very minute. There are some 
even on the anal system. ‘The only other form seen was in a Fakarava Island 
specimen (Pl. 27, figs. 1, 2), where near the actinostome a few of them are lance- 
olate. The serrations on these spines from near the actinostome, frequently stop 
short of the distal end in specimens from the Barbados (PI. 27, fig. 15) and Jamaica 
(Pl. 27, fig. 25). 
THE LANTERN AND AURICLES. 
Plate 11, figs. 1, 2, 7, 8; Plate 12. 
Of the various specimens brought from Port Antonio, Jamaica, a small 
number were nearly, or but a little over, five millimetres in length; only four, 
provided with a masticatory apparatus, were under this measurement. Consid- 
ering that they had been a few days in alcohol, when the preparations were made, 
they showed the various parts, including the pigmented sack that holds the 
lantern (PI. 11, figs. 7, 2), very well. The lower end of this sack is probably 
joined to the buccal membrane by a small neck; it contains a few caleareous 
particles close to the teeth (Pl. 11, fig. 4). In just what manner this sack passes 
the pentagonal muscular band of the summit of the lantern, and whether it is 
connected with the oesophagus which goes through its centre where the com- 
passes meet, could not be ascertained, as the diameter of the lantern was only 
1.24 mm. and too fragile for dissection. The calcareous parts of the whole 
apparatus are fairly solid, and not quite so delicate as the valves of the pedi- 
cellariae. To each of the primordial interambulacral plates are attached a pair 
of strong muscles (PI. 11, fig. 2), each with two branches at the upper end, one 
of which is fastened to the compass, the other apparently to the brace. The 
lower end of each half pyramid is also connected by two muscles to the rudimen- 
tary auricle, and its ambulacral plate. After being denuded of their spines, the 
smallest specimens having a lantern, were only 3.70 mm. in length (Pl. 11, 
fig. 1), and the largest 4.25; in the latter (PI. 11, fig. 8), the volume of the dental 
apparatus filled about one sixth of the space inside the test. The next available 
size was 5.16 mm. in length (Pl. 11, fig. 9), and lacked not only the masticatory 
apparatus, but the auricles also (Pl. 11, fig. 10)... It seems very unlikely that 
* The statement (Amer. journ. sci., 1909, ser. 4, 28, p. 490) that the small auricles are present is 
erroneous. 
