40 THE NAUTILUS. 
ON A NEW SPECIES OF MYLLITA. 
BY, W., HaeDALL. 
The genus Myllita was founded in 1850 by d’Orbigny and Récluz 
on a species named by Récluz VW. Deshayesii, which was subsequently 
wrongly united to Pythina Hinds by Adams and others. This 
error was pointed out by E. A. Smith in a discussion of the genus 
Pythina in 1891. The original authors wrongly ascribed a tri- 
angular pallial sinus to Myllita. The name was subsequently 
changed to Mylitta by Kobelt but there does not seem to be ground 
for the assumption that the original name was based on that of the 
city. The essential characters of the genus are as follows: 
Shell small, equivalve, with a small anterior and posterior dorsal 
gape, with an obsolete external amphidetic ligament and a strong 
internal resilium, the latter with a mesial calcareous coating; pallial 
line simple, with rather large adductor scars ; foot strong, byssifer- 
ous ; the young incubated, as in Kellia, within the mother’s tissues, 
numerous, vitreous, smooth ; the adult strong, with concentric and 
radiate or divaricate sculpture, the surface more or less punctate or 
sagrinate; hinge with, in the left valve single lateral laminze in 
front and behind, with a /\-shaped or petaloid cardinal ; the right 
valve is similar but with double laterals, the resilium set in a well 
marked suleus below the ventral posterior lamina. Type J. 
Deshayesii Récluz. 
Two species have since been described as Pythina: Myllta tas- 
manica Tension- Woods (1875) from Tasmania and M. Stowet Hutton 
(1873) from New Zealand. The former proves from authentic speci- 
mens to be quite distinct from If. Deshayesii. Smith added, in 
1891, M. auriculata from Tasmania. 
M. Deshayesii has the right cardinal merely grooved, not /\-shaped ; 
in M. tasmanica both are conspicuously /\-shaped. In M. Stowei the 
right cardinal is small, slender and simple, the anterior lamin very 
short and stout, the posterior laminz quite long and slender. The 
resilium in the latter is rather short, and there is a small impressed 
lunule over the dorsal anterior lamina. In all, the external ligament 
is feeble but present and amphidetic. The following new species is 
in the collection of the Academy of Natural Sciences Philadelphia. 
