THE BURROWING BARNACLES (CIRRIPEDIA: ACROTHORACICA) 55 



shell is no longer surprising, but the distinction of L. mitis is clouded by 

 the possibiUty that it might be an immature form of L. spinatus. 



The most obvious difference between the two species is in the 

 opercular armament. The pronounced hook and articulated spine in 

 mature L. spinatus females is characteristic, but develops rather late 

 in life. 



A careful search for intermediate forms was undertaken and in all 

 cases the specimens could clearly be designated L. spinatus or mitis in 

 the samples listed above. 



Size determinations were made on five L. mitis and three L. spinatus 

 from the same piece of coral from Ponape. The L. mitis measured an 

 average 2.08 X 1.15 mm in length and Avidth, with an aperture of 

 0.80 mm. The range of each was 1.75-2.38 X 0.80-1.38 and 0.63-0.98. 

 The L. spinatus was 3.75 X 2.05 and 1.21 mm, respectively, with a 

 range of 3.0-4.5 X 1.65-2.50 and 1.00-1.50 mm. As you can see, there 

 is no overlap in the ranges. That the L. mitis was not just young 

 L. spinatus is attested by the fact that three of the five specimens of 

 L. mitis were gravid with eggs, and were thus obviously sexually 

 mature. The Kwajalein material gives some overlap. A L. mitis 

 specimen measured 2.84 X 1.58 mm with aperture of 0.99 mm, while 

 the measurements of a well-developed L. spinatus from the same shell 

 is 2.39 X 1.31 and 1.13 mm. 



In relationships, I would place L. mitis very close to L. spinatus, 

 and not quite as close to L. habei. 



It is noteworthy that there are many collections of L. spinatus which 

 are exclusively this species and have no specimens resembling L. mitis. 

 L. mitis is not found in association with L. habei, which is a western 

 Pacific species. L. mitis is a central Pacific form, from Fiji to the 

 Caroline and Marshall Islands. 



Lithoglyptes scamborachis, new species 



Figure 10 



Diagnosis: Lithoglyptes with operculum armed with one pair 

 of medial spines bent anteriorly or laterally at the tips, and one stout 

 toothed cone on the left side posteriorly. One pair of weak lateral 

 bars and one prominent posterior apertural bar present. Apertural 

 length 63 percent of greatest width of body. Caudal appendage 

 two-segmented. 



Etymology: scamb- (Gr.), curved, bent, ra^his (Gr., or rha^^his), 

 a spine, because of the bent spines on the operculum. 



Distribution: Six specimens were found in one valve of Tridacna 

 maxima Roding from Heron Island, Queensland, Australia. Two 



