The authors present a detailed and interesting account of the anatomy of the lungfish cornea. Given their phylogenetic position and their ecology, lungfish may provide important information about the evolution of corneal structure of sarcopterygians.

I noticed a series of outdated phylogenetic terms, specifically the use of “primitive” and “kingdom” that should be updated:
1) “thought to be the most primitive species of extant lungfishes having changed little over the last 100 million years”
2) “it may be a primitive characteristic in the evolution of the cornea”
3) “vertebrate kingdom”
In the first example, I suggest replacing “primitive” with “earliest-branching”. There is no correlation with “advancement”. As for the second example, replace “primitive” with ancestral. Finally, instead of vertebrate “kingdom”, just say vertebrates or Vertebrata.

I also noticed that the phylogenetic position of Neoceratodus forsteri is misinterpreted:
“is currently believed to represent the closest living relative to land vertebrates”
As lungfishes (Ceratodontiformes) are monophyletic, they are all equally related to tetrapods.

As a final suggestion regarding phylogenetic and evolutionary nomenclature, I suggest rewording the following sentence:
“Tetrapods, including all landliving vertebrates, are thought to have evolved from lobe-finned (sarcopterygian) fishes that developed adaptations for an amphibious existence (Friedman, 1969).”
Tetrapods are sarcopterygians, and develop is not synonymous with evolve. Possible wording: Tetrapods, which are phylogenetically nested within sarcopterygians, evolved adapatations …”. A few recent papers on phylogeny of sarcopterygians should be added; Friedmann 1969 by itself is insufficient.

Below I am listing a few specific questions that I hope the authors can address. Many of these questions aim to improve the functional interpretations and explanations thereof:

“Although the eyes of N. forsteri have relatively low spatial resolving power (1.6–1.9 cycles deg-1), based on the spacing of their large ganglion cells, they have retained the ability to resolve objects (Bailes et al., 2006b)”
What kind of objects can be resolved with a spatial resolution of less than 2 cycles/deg in highly turbid environments?

“Some previously preserved ocular and corneal tissue was also donated by J. Joss and N. A. Locket.”
I think we would need to know animal ethics permits for these specimens?

“The corneal epithelial cell density (7,834 cells/mm2) of N. fosteri is considerably less than most other teleosts”
Neoceratodus forsteri is not a teleost.

“similar to densities found in many species of (non-aquatic) birds, amphibians, reptiles and mammals”
Are there any data on secondarily aquatic tetrapods? Perhaps add a table with references?

“The function of lamellar branching and anastomosing, including in N. forsteri, is thought to maintain the orthogonal and rotational organisation of the collagen lamellae for transparency under various environmental conditions.”
How would this work? Is there a source for this hypothesis, or is it a new idea?

“This finding may explain the large diameter of the retinal photoreceptors in N. forsteri, which will improve its ability to visually discriminate between the macrophytes on which it feeds (Hellström et al., 2011).”
How would a larger diameter of photoreceptors improve visual discrimination? This seems counterintuitive.

“Another function of Desçemet’s membrane may be to distribute even tension and prevent gross deformation of the cornea after swelling (S. P. Collin & Collin, 1993)”
Similar to my questions above: how would that work? Is there a possible mechanism? How could this be tested?

“The presence of lamellar branching and anastomosing may also play a role in the prevention of corneal swelling”
One more question that probes at the functional interpretation of these structures: how would that work, exactly? Possible mechanism?