Thoracic Cirripedia from a Guyot — Zullo and Newman 
359 
conspicuous; surface clothed sparsely throughout 
with long, soft setae and an occasional short 
spine; distal end supporting numerous long, 
soft setae which obscure details of apex; surface 
irregular and lumpy, no annulations observable. 
TYPE DESIGNATION: Holotype: UCMP 37860. 
Paratypes: UCMP 37861, 37862. Additional 
specimen: U.S. National Museum, Washington 
D.C, no. 109781. 
DISCUSSION: The status and definition of the 
genus Megalasma, especially of the less clearly 
defined subgenus Megalasma (Glyptelasma ) , 
has been discussed and emended by a number 
of authors, particularly Caiman (1918, 1919). 
Kruger (1940:29, table 1) indicates that at 
least five species of the subgenus Megalasma 
(Megalasma) have been described. These can 
be divided into two series: "Striatum,” the type 
species of the genus and subgenus, and "Minus” 
the second form of the subgenus to be described. 
The latter series may contain as many as three 
species. However, the views of Barnard ( 1924) , 
Nilsson-Cantell (1938), and Utinomi (1958), 
when taken together, suggest that there is only 
one species contained in the Minus complex. 
The inclusion of M. striatum in a portion of 
the M. minus synonymy by Weltner (1922) is 
apparently by lapsus calami. The present report 
is not directly concerned with the "Minus” 
synonymy, having no additional data, and simply 
follows the synonymy proposed by these workers: 
1. Megalasma (Megalasma) striatum Hoek, 
1883 
2. Megalasma (Megalasma) minus Annan- 
dale, 190 6b 
Megalasma striatum minus Annandale, 
190 6b 
Megalasma lineatum Hoek, 1907 
? Megalasma bellum (Pilsbry, 1907c) 
? Megalasma carinodentatum Weltner, 
1894 
The two series are closely related, differing in 
proportions and details of the articulations of 
the valves. Following the views of Pilsbry 
(1907c) and Broch (1922), the degree and 
specialization in armament seen in Megalasma 
s. str. has progressed, from Poecilasma through 
Glyptelasma. The most highly developed form 
is Megalasma striatum, in which the terga are 
enlarged (a condition that reduces the relative 
height of the carina to half the height of the 
entire capitulum) and the lateral margins of 
the distal portions of the carina are strongly 
developed articular surfaces. It is to the striatum 
section of the subgenus that the new species 
described here belongs. 
Megalasma (Megalasma) striatum is very 
similar to the form described here. The lateral 
view of M. (M.) striatum depicted by Hoek 
(1883, pi. 2, fig. 5) and Broch (1922, text 
fig. 29) shows a ridge of coarse beads or eleva- 
tions running in an arc across the basal portion 
of the scutum from the umbo to the lateral 
margin. The arc then continues to the basal 
portion of the carina and terminates at its umbo. 
The dorsal aspect given by Hoek (loc. cit., pi. 2, 
fig. 6) does not show the course of this beaded 
ridge on the carina as one would expect, but 
only a peculiar elevation formed along the lateral 
margin of the scutum. At first inspection it 
would appear that Gruvel (1905, text fig. 126) 
had merely traced Hoek’s drawings; however, 
the dorsal aspect of the basal portion of the 
carina is considerably different than that illus- 
trated by Hoek. It shows clearly the course of 
the beaded ridge extending outwardly from the 
carinal umbo. The form described here clearly 
lacks this ridge as viewed from both lateral and 
dorsal aspects. The basal portion of the scutum 
(Fig. 2 A) is essentially smooth, unmarked by 
beads or ridges. The basal portion of the carina 
(Figs. 2 A, B) also lacks the ridge seen in M. 
(M.) striatum figured by Hoek, Gruvel, and 
Broch, but below this area there are approxi- 
mately 6 rows, each of 2-10 short ridges, run- 
ning to the basal margin. 
Of the trophi only minor differences were 
found. The lower angle of the mandible, includ- 
ing the fourth tooth (Fig. 2 F), is much more 
strongly produced than that figured by Hoek 
(loc. cit., pi. 1, fig. 8) and by Utinomi (loc. cit., 
text fig. 4b) for Megalasma (Megalasma) stri- 
atum. The notch of the first maxilla (Fig. 2 G) 
is less pronounced and the setae clothing its 
surface are short and weak, appearing vestigial. 
The second maxilla is longer than high, probably 
corresponding to the proportionately greater 
length of the mandible. 
The ctenopod chaetotaxis (Fig. 2 H) appears 
the same as that of Megalasma (Megalasma) 
striatum. However, in the new species the major 
