Laube stated (op. cit.) that there is a spectacle-shaped fascicle in Hemipatagus; and then R. Etheridge, jun., in 1775, writes, "Below the anal orifice is a spectacle-shaped fasciole carrying on each side a circlet of primary perforated tubercles." They thus brought the genus into actual identity with Maretia, which, however, was not known then to be represented in any fossiliferous deposits, and which was supposed to be a recent form.
Recent investigations upon some wonderfully perfect specimens have enabled me to add to Laube's discovery the existence of an internal fasciole; and it is therefore necessary to take the group away from Spatangus and Maretia, according to the ordinary rules of classification (although much may be said to the contrary in a classification founded on heredity), and to place it in the neighbourhood of Breynia and Echinocardium, under the head of Lovenia, Desor.
Lovenia has the following characters:—
Test thin, elongate, arched, flattened, truncated posteriorly. Large tubercles upon the upper or abactinal surface, but not on the posterior interambulacrum; and they are situate in deep and large scrobicules. The ambulacral petals, in somewhat triangular and adjoining zones, form two cresents on each side of the apex. There are four generative pores; and the anal system is more or less sunken in the posterior truncation. The anterior groove is slight. The actinal surface has large and other tubercles in deep scrobicules, forming a close pavement laterally; the posterior end of this surface is ornamented with regularly placed small tubercles; and the floscelles are distinct but small. There is an internal fasciole and a subanal spectacle-shaped fasciole.
The species hitherto described are Lovenia cordiformis, Lütk., from Guayaquil and the Gulf of California, Lovenia elongata, Gray, Red Sea, Australia, and Philippines (Lovenia hystrix is probably the same as this), and Lovenia subcarinata, Gray, from China, Japan, and the Sandwich Islands.
A comparison of the details of some beautifully preserved specimens of Echini from the Section at Mordialloc, on the east shore of Port- Phillip Bay, which would have been classified as Hemipatagi, with the diagnostic characters of Lovenia, proves the generic identity. In most specimens which have hitherto been collected, described, and figured, the surface has been exposed to attrition and weathering, and more or less of the fine miliary ornamentation which covers the whole abactinal surface has been removed. In many specimens there is not a trace of it left, and the divisions between the plates have become evident. This fine ornamentation reaches to the ambitus, where it becomes coarser, and gradually enlarges on the actinal surface until the large primaries are reached; but around the anal opening the ornamentation becomes finer, and the miliaries are smaller and wider apart. The internal fasciole is composed of tubercles of about one sixth the size of the finest miliaries; and those of the subanal fasciole are quite as small.
