Geology and Natural History. 



any consequence ig reported 



iiie phenomena seem to me to point to a center of disturbance 

 to the leeward of the islands, |)erhaps at the center of the circle 

 of wliich the islands form an are, and at a ureat depth. liut as 

 you 8te, our data are as yet very imperfect. There ha\e been 

 several slio-ht shocks felt here since, on the 22d and 24th. I can- 

 not learn that there is any unusual action goino- on at Kilauea or 

 iu Mokuaweoweo. 



I am hoping to commence the survey of these islands next May. 



4. Xoteon Trinierelki a<m,vinata ;\)j \L Uiua-;g^. (Communi- 

 cated by the author).— The genus TrimereUa was founded by me 

 on two species, T. grandis and T. aemninata ; but of the latter I 

 had only the rostral half of the vontral valve of :i sniall sjKrhnen. 

 I therefore named it provisionally and stated that it ditiered 



pointed, and the longitudinal septa running all the way to the 

 beak." (The septa here alluded to and the walls between the 

 tubes mentioned below). Within the last few days ."' "" " 



It then immediately became evident that several separate dorsal 

 v^alves in our collection belonged to the same species. I have, 

 therefore, now abundant material to illustrate the species, which 

 i shall do soon, but iu the meantime propose to notice its leading 

 characters briefly. 



The ventral valve, in young specimens, is somewhat straight 

 •'joug the median line, but becomes more and more arched as the 

 ^ize mcreases. It is ovate, rounded in front, widest a little in 

 'I'lvanee of the mid-length, thence tapering with nearly straight 

 swes to the beak which is narrowly rounded,— almost acute. In 

 tile substance of the shell there are two large tubes, which extend 

 trom about the middength to the beak, these are joined in the 

 beak by two others, one on each side. All of these tubes are open 

 anteriorly, but closed at their terminations in the beak. The area 

 18 large, concave and transversely striated. The dorsal valve is 

 niQch shorter than the ventral, more convex and has its beak 

 ]vJ ^t^*^"gly incurved. It has two tubes which extend nearly to 

 ■'the beak. The shell is marked Avith coarse < 



accretion ridges of growth. Length of the largest specimen 3^ 

 inches, width :i inches. The above is sufficient to show that this 

 ^Jecies is quite distinct from T. grandis. If a section were to be 

 made across the beak of a perfect shell of T. acuminata, it would 

 ^.How four perforations arranged in a curve, exactly as in the 

 ^nular section of the Swedish species figured by Dr. Lindstrom. 

 f «t If the beak of T. grandis were to be cut across, it would 

 snow only two orifices, and they would be the homologues of the 

 t^o lateral perforations in the section of T. acuminata, because in 

 l' grandis the two central tubes do not extend, into the beak, 

 ^^^t terminate before they reach it. 



